Physics I PLV's and HW

1b) Which of the following is true concerning the relationship between the total distance an object moves and the displacement of the object? The displacement is always less than the total distance. The displacement will be less than or equal to the total distance. The total distance will be less than or equal to the displacement. The total distance is always less than the displacement. The total distance and displacement are always equal.

The displacement will be less than or equal to the total distance.

2b A pushing force of 10 000 N is applied to the backside of a car at an angle of 25.0° above the horizontal, moving the car through a horizontal distance of 15.0 m. If the car has a mass of 2 250 kg, what is its final speed? 7.80 m/s 11.0 m/s 121 m/s

11

2b) Consider two people on the surface of the earth. One is on the equator, and the other is at the North Pole. Which person experiences the larger centripetal acceleration? -Both experience the same centripetal acceleration. -The person at the equator. -The person at the North Pole.

-The person at the equator.

7b What is the maximum height a 100-W engine can lift a 100-kg man in 3.00 minutes? 10.0 m 9.80 m 36.8 m 18.4 m

18.4 m

You are using a wrench and trying to loosen a rusty nut. Which of the arrangements shown is most effective in loosening the nut?

2

8 A projectile is launched with a momentum of 200 kg •m/s and 1000 J of kinetic energy. What is the mass of the projectile? 20 kg 40 kg 5 kg 50 kg 10 kg

20

1b) An object is undergoing uniform circular motion. Which of the following changes would increase the period of the motion? I. Increase the radius of the circular motion. II. Decrease the radius of the circular motion. III. Increase the speed of the object. IV. Decrease the speed of the object.

I and IV (uniform circular motion is the time it takes to complete one revolution/go around the circle once)

A small cylinder rests on a circular turntable that is rotating clockwise at a constant speed. Which set of vectors gives the direction of the velocity v and acceleration a of the cylinder, and the net force ΣF that acts on it. 3 1 4 2

4

5a In which of the following is a tangential acceleration involved in the motion? A runner running at a constant 4 m/s around a circular track The tip of a lawn mower blade running at constant 40 rev/s A 1-kg mass swinging freely at the end of a rope The outer edge of merry-go-round ride rotating at a constant 30o/s

A 1-kg mass swinging freely at the end of a rope

1b A pushing force of 10 000 N is applied to the backside of a car at an angle of 25.0° above the horizontal, moving the car through a horizontal distance of 15.0 m. What is the work done by the force?

1.36 x 10 ^5 J

At the bowling alley, a 4 kg ball is rolling back towards the ramp at a speed of 2 m/s. The ramp leads the balls to a chute 0.5 m above the base of the ramp. Will the ball make it up the ramp? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Yes b no c not enough info

no

8a) Consider the vector equation A + B = C . The component method of vector addition specifies that the scalar components of the resultant vector C are given by Cx = Ax + Bx and Cy = Ay + By. Which of the following would give the magnitude of the resultant vector C?

sqrt of Cx^2 + Cy^2

3a What is the work done by the force of gravity when a 20.0-kg weight is displaced vertically upward a distance of 3.0 m? 600 J -600 J 0 J

- 600

11) A physics student standing on the edge of a cliff throws a stone vertically downward with an initial speed of 10.0 m/s. The instant before the stone hits the ground below, it is traveling at a speed of 30.0 m/s. If the physics student were to throw the rock horizontally outward from the cliff instead, with the same initial speed of 10.0 m/s, what is the magnitude of the velocity of the stone just before it hits the ground? The height of the cliff must be specified to answer this question 20.0 m/s 10.0 m/s 30.0 m/s 40.0 m/s

**they're going the same distance so it'll be the same

4a if the angular speed of a 1.1-m baseball bat is 2.0 rad/s, what is the tangential speed of the tip of the bat? 1.1 m/s 6.9 m/s 2.2 m/s 13.8 m/s

2.2 m/s

8b If the chemical energy stored in a 250-Calorie (1.0 × 106 J) energy bar were converted into the kinetic energy of a 2 200-kg car, what would be the speed of the car (assuming it started from rest)? 21.3 m/s 909 m/s 60.4 m/s 30.2 m/s

30.2 m/s

7a How much energy is dissipated by a 60-W light bulb in one minute? 60 J 3600 J 360 J

3600 J

If each tug-of-war team pulls with a force of 400 N, what is the tension in the rope? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a 0 N b 400 N c 800 N d 1600 N

400 N

5b what is the magnitude of the total acceleration of the tip of a 1.20-m (radius) airplane propeller that is moving with an angular speed of 6.00 rad/s and undergoing an angular acceleration of 14.0 rad/s^2? 16.8 m/s^2 138 m/s2 46.4 m/s2 43.2 m/s2

46.4 m/s2

3a) A car is traveling in uniform circular motion on a section of flat roadway whose radius is r . The road is slippery, and the car is just on the verge of sliding off the roadway. If the car's speed were now doubled, what would be the smallest radius of the curve it could drive on without slipping?

4r

2 How much energy is dissipated in braking a 1200-kg car to a stop from an initial speed of 30 m/s? 540000 J 12000 J 280000 J 820000 J 24000 J

540000 J

7 The initial velocity of a 4.0-kg box is 11 m/s, due west. After the box slides 4.0 m horizontally, its speed is 1.5 m/s. Determine the magnitude and the direction of the non-conservative force acting on the box as it slides. 59 N, due east 120 N, due east 83 N, due west 42 N, due west 31 N, due east

59 N, due east

3 A 2.0-kg projectile is fired with initial velocity components vox = 30 m/s and voy = 40 m/s from a point on the earth's surface. Neglect any effects due to air resistance. What is the kinetic energy of the projectile when it reaches the highest point in its trajectory? 4900 J 1600 J zero joules 900 J 2500 J

900 J

1a The figure shows an overhead view of a large door that is free to pivot on a hinge along its left edge. A force is applied to the door in four different ways. The magnitude of the force is the same in each case. In which case is the torque on the door the largest?

A

Three identical projectiles are fired at different launch angles and with different initial velocities. Which projectile has the greatest potential energy, when its at the peak in its trajectory? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a A b B c C

A

3b) Which of the following is/are true? I. The centripetal force points in toward the center of the circular motion. II. The centripetal force is independent of the object's mass. III. The centripetal force points in the opposite direction as the centripetal acceleration. IV. The centripetal force is a new and separate force created by nature, and therefore should appear in a free-body diagram.

I only

1a) An object is undergoing uniform circular motion. Which of the following is/are true? I. The object is moving at constant velocity. II. The object is moving at constant speed. III. The object is accelerating.

II and III (the object's direction is constantly changing so it is accelerating)

1b A group of particles has a net momentum equal to zero. Which of the following must be true? I. The speed of each particle is zero.II. The velocity of each particle is zero.III. The mass of each particle must be equal.IV. The kinetic energy of each particle must be zero. I and III I and IV IV only II only None of the above is true. I only III only

None of the above is true.

4b) Three swimmers can swim equally fast relative to the water. They have a race to see who can swim across a flowing river in the least time. Swimmer A swims perpendicular to the current and lands on the opposite shore downstream, because the current has swept him in that direction. Swimmer B swims upstream at angle to the current, so that when she reaches the other side, she is straight across from where she started. Swimmer C swims downstream at an angle theta in an attempt to take advantage of the current. Who crosses the river in the least time?

Swimmer A To get to the other side, each swimmer must cover a distance perpendicular to the shore that is equal to the width of the river. The swimmer with the greatest velocity component perpendicular to the shore will cover this distance in the shortest time.

1b Two forces are applied to a ship's wheel. The wheel is not rotating. Which of the following must be true? F1 must be equal to F2 The magnitude of the torque created by F1 must be equal in magnitude to the torque created by F2 The magnitude of the torque created by F1 must be greater than the magnitude of the torque created by F2. The magnitude of the torque created by F2 must be greater than the magnitude of the torque created by F1 .

The magnitude of the torque created by F1 must be equal in magnitude to the torque created by F2

2a) At t = 0, an object is moving with constant velocity in the xy plane, where its velocity vector makes an angle of 45° relative to the positive x axis. The object then accelerates for 2 seconds in the positive y direction only. After the 2 seconds, which of the following is true? The velocity vector of the object is directed at an angle greater than 45° above the positive axis. The velocity vector of the object is directed at an angle less than 45° above the positive axis. The velocity of the object is zero. The velocity vector of the object is still directed at 45° above the positive axis.

The velocity vector of the object is directed at an angle greater than 45° above the positive axis.

8b) You are standing on a scale and in a fast elevator that is taking you to the top of a tall building. The elevator slows as it reaches the top. What is true of your apparent weight as the elevator decelerates? Your apparent weight is less than your true weight. Your apparent weight is equal to your true weight. Your apparent weight is greater than your true weight.

Your apparent weight is less than your true weight.

A moving van collide with a sports car in a high-speed head-on collision. Crash! During the impact, the truck exerts a force F_truck on the car and the car exerts a force F_car on the truck. Which of the following statements about these forces is true: Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a F_truck on car = F_car on truck b F_truck > F_car on truck c F_truck < F_car on truck d (Are you out of your mind ? ) Not enough information!!!!!

a F_truck on car = F_car on truck

An object is in uniform circular motion. At point O it is released from its circular path. Where does it go? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Nowhere, the object stays at O b Moves in a straight path between O and A c Moves along the circular arc between points O and P

b Moves in a straight path between O and A

An elevator is going up at a constant speed. Near the top floor, it starts to slow to a stop. During the period that it is slowing down, its acceleration is: Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a downward b upward c neither

downward

2a A 90.0-kg man runs at a constant speed of 11.5 m/s. What is his kinetic energy? 5 950 J 1 035 J 11 900 J

first

2a) Which of the following does NOT represent an inertial frame of reference? -An airplane in straight and level flight at a constant speed. -A skydiver falling straight downward at a constant (terminal) speed. -A boat moving at a constant speed along a straight path. -A car going around a circular track at a constant speed.

-A car going around a circular track at a constant speed.

9a) Suppose the coefficients of static and kinetic friction have values such that us= 1.4 uk for a crate in contact with a cement floor. Which of the following statements is true? -The magnitude of the static friction force on the crate is always 1.4 times as large as the kinetic friction force. -The magnitude of the kinetic friction force on the crate is always 1.4 times as large as the static friction force. -The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force.

-The magnitude of the maximum static friction force on the crate is 1.4 times as large as the kinetic friction force. **Remember that the maximum static friction force and the kinetic friction force are both directly proportional to the normal force.

2b) In which location does a 15-kg bowling ball have the smallest mass? -In deep space where there is no force due to gravity. On Earth. -The mass is the same everywhere. -On the moon where the force due to gravity is less than -on earth.

-The mass is the same everywhere.

3a) The net external force acting on an object is zero. Which of the following statements is/are true? -The object can only be traveling with a velocity that is changing. -The object can only be traveling with a constant velocity. -The object can only be stationary. -The object can be either stationary or traveling with constant velocity.

-The object can be either stationary or traveling with constant velocity.

6b -A rock is thrown vertically. What is true when the rock reaches its maximum height? -The velocity is zero, and the acceleration is -g -The velocity equals half its initial velocity, and the acceleration is zero. -The velocity equals half its initial velocity, and the acceleration is -g -The velocity is zero, and the acceleration is zero.

-The velocity is zero, and the acceleration is -g

4) Which statement is true regarding a jet moving at a constant speed of 450 m.p.h. in straight and level flight. -With no net force, the jet would lose altitude. -There is a net force acting on the jet, but only in the upward direction - otherwise it could not maintain flight. -There is no net force acting on the jet. -With no net force, the jet would eventually slow down.

-There is no net force acting on the jet.

3aA projectile is launched in the air and follows the parabolic path shown. When it reaches the peak in its trajectory, what is the acceleration of the projectile?

-g m/s^2

4) The velocity of a train is 80.0 km/h, due west. One and a half hours later its velocity is 65.0 km/h, due west. What is the train's average acceleration? 43.3 km/h2, due east 43.3 km/h2, due west 53.3 km/h2, due east 10.0 km/h2, due east 10.0 km/h2, due west

10.0 km/h2, due east

1a) Which of the following is/are true? I. Force is a scalar quantity. II. Force is a vector quantity. III. A force is a push or a pull between objects that occurs only when the objects are in physical contact. IV. Non-contact forces are also called action-at-a-distance forces.

11 and IV

2b) A powerboat, starting from rest maintains a constant acceleration. After a certain time t , its displacement and velocity are r and t. At time 2t, what will be its displacement and velocity, assuming the acceleration remains constant? 4r and 4v 4r and 2v 2r and 4v 2r and 2v

4r and 2v **Notice that for a constant acceleration, the displacement is proportional to t^2, and the velocity is proportional to t .

1b) Which of the following is/are true? I. Mass is a vector quantity. II. Mass is a scalar quantity. III. Mass is a measure of how much matter an object contains .IV. There is no relationship between force and mass. V. Isaac Newton developed three important laws of motion that describe the relationship between force and mass.

II, III, and V

A person starts in Boulder, drives to Denver (50 km away) in 1 hour, stays in Denver 1 hour, then speeds back to Boulder in 30 minutes. What is the average velocity of the round trip? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a 25 km/h b 67 km/h c 40 km/h d 75 km/h e none of these

None of these

Suppose you are driving a convertible with the top down. The car is moving to the right at constant velocity. You point a rifle straight up into the air and fire it. In the absence of air resistance, where would the bullet land - behind you, ahead of you, or in the barrel of the rifle? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Behind you b ahead of you c in the barrel

in the barrel

2 Five hockey pucks are sliding across frictionless ice. The drawing shows a top view of the pucks and the three forces that act on each one. The forces can have different magnitudes (F, 2F, or 3F), and can be applied at different points on the puck. Only one of the five pucks could be in equilibrium. Which one?

-4 -For the puck to be in equilibrium, the sum of the torques about any axis must be zero (Στ = 0). Select an axis that passes through the center of the puck and is perpendicular to the screen. The forces 2F and 3F exert a net torque about this axis, so the puck cannot be in equilibrium.

6b A 2 000-kg car travelling at 25.0 m/s skids to halt on level ground. How much work was done by nonconservative forces in stopping the car? -6.25 × 105 J 6.25 × 105 J 0 J

-6.25 × 105 J

2a Which of the following is true about a rigid body in dynamic equilibrium? The body cannot have translational motion, but it can have rotational motion. The body can have translational motion, but it cannot have rotational motion. The body cannot have translational or rotational motion of any kind. The body can have translational motion and rotational motion, as long as its translational and angular accelerations are equal to zero.

-The body can have translational motion and rotational motion, as long as its translational and angular accelerations are equal to zero.

7a) A stone is tied to a string and swung along the path of a vertical circle at constant speed. When is the string most likely to break? -When the string is horizontal. -The string is equally likely to break for any position of the stone. -When the stone is at the very top of the circle. -When the stone is at the very bottom of the circle.

-When the stone is at the very bottom of the circle. *if you drew out the FBD of this you would see that tension has the highest value when the rock is at the bottom.

3b A stone sphere of radius 7.00 m rests in a flat field. Relative to the ground, what is the gravitational potential energy of a 90.0-kg person sitting on the very top of the sphere? 3.88 × 104 J 1.23 × 104 J 7.76 × 104 J

1.23 × 104 J

2b Exploding gunpowder in a cannon (mass ) propels a cannonball (mass ) forward. Simultaneously, the cannon recoils. Which of the following is true? Note that .I. The speeds of the cannonball and cannon are equal.II. The magnitudes of the momentum of the cannonball and cannon are equal.III. The kinetic energy of the cannonball and cannon are equal. II only III only II and III I only I and III

11 only

17 A 3.00-kg model airplane has velocity components of 5.00 m/s due east and 8.00 m/s due north. What is the plane's kinetic energy? 38 J 96 J 134 J 254 J

134 J

5a A stone is dropped from rest from the top of a cliff into a pond below. If its initial height is 10 m, what is its speed when it hits the water? 9.9 m/s 14 m/s 4.8 m/s

14

12) Which of the following describe nonequilibrium conditions in the context applying Newton's laws of motion? A spacecraft decelerating upon reentry into the atmosphere. A car accelerating through a traffic light. A ball falling off the roof of a house. A roller coaster going over the crest of a hill. All of the above.

All of the above. (they're all undergoing acceleration)

4a) Two cars are identical except for the tread design on their tires. They both enter an unbanked horizontal curve at the same speed. Car A cannot negotiate the turn (it slides off), but Car B can. Which tread design, the one on Car A, or the one on Car B, yields the larger coefficient of static friction between the tires and the road? Car B Car A Cannot be determined from the given information.

Car B

You are given two carts, A and B. They look identical, and you've been told they are made of the same material. You place A at rest on an air track and give B a constant velocity to the right so that it collides elastically with A. After the collision, both carts move to the right, the velocity of B being smaller than what it was before the collision. What do you conclude? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Cart A is hollow. b The two carts are identical. c Cart B is hollow.

Cart A is hollow

15 A circular hula hoop rolls upright without slipping on a flat horizontal surface. Which one of the following statements is necessarily true? Every point on the rim of the wheel has a different velocity. All points on the rim of the hoop have acceleration vectors that are tangent to the hoop. All points on the rim of the hoop have the same velocity. All points on the rim of the hoop have acceleration vectors that point toward the center of the hoop. All points on the rim of the hoop have the same speed.

Every point on the rim of the wheel has a different velocity.

7a) True or False: If the magnitudes of both the x- and y-component of a vector are doubled, then the magnitude of the vector is also doubled.

True

A young girl wishes to select one of the frictionless playground slides below to give her the greatest possible speed when she reaches the bottom of the slide. Which one should she choose? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Slide 1 b Slide 2 c Slide 3 d Slide 4 e Any of them

any of them

4a True or False: In a two-dimensional collision, momentum can only be conserved in one dimension, not both. False True

false

A ball has a speed of 15 m/s. Only one external force acts on the ball. After the force acts, the ball's speed is 7.5 m/s. The force on the ball did: Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a positive work b negative work c no work

negative work

2a What is the average angular velocity of the seconds hand of a clock? w= 0 w= -2 rad/s w= 2 rad/s w= -0.10 rad/s w= 0.10 rad/s

w= -0.10 rad/s

A rock of mass m is twirled on a string in a horizontal plane. The work done by the tension in the string on the rock is.. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Positive b negative c zero d neither of the above

zero

An object is lowered by a rope at a constant speed. The net force on the object is: Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a upward b downward c zero d not enough information

zero

1. The drawing illustrates an overhead view of a door and its axis of rotation. The axis is perpendicular to the screen. There are four forces acting on the door, and they have the same magnitude. Rank the torque τ that each force produces, largest to smallest.

τ3, τ2, τ1 and τ4 (a two-way tie) The torque τ3 is greater than τ2, because the lever arm for the force F3 is greater than that for F2. The lines of action for the forces F1 and F4 pass through the axis of rotation. Therefore, the lever arms for these forces are zero, and the forces produce no torque.

3a Which of the following sets of variables are suitable for direct substitution into the angular kinematic equations? Wo= 0 rev/s, w= 5.0 rad/s, 4.0 s Wo= 2.0°/s, a= 2.5 rad/s2, 25° W= 5.0 rev/s, a= 2.5 rad/s2, 25° Wo= 0 rad/s, w= 5.0 rad/s, 3.0 s

**hard to do this one bc some of the variables don't format properly. Look on sheet Wo= 0 rad/s, w= 5.0 rad/s, 3.0 s

23) The drawing shows three blocks, each with the same mass, stacked one upon the other. The bottom block rests on a frictionless horizontal surface and is being pulled by a force F that is parallel to this surface. The surfaces where the blocks touch each other have identical coefficients of static friction. Which one of the following correctly describes the magnitude of the net force of static friction fs that acts on each block? fs,A = 0 and fs,B = fs,C/2 fs,A = fs,B = fs,C fs,A = fs,B = fs,C/2 fs,C = 0 and fs,A = fs,B/2 fs,A = fs,C = fs,B/2

*The first is wrong bc it states that the net frictional force acting on block A is zero, which implies that the surfaces where blocks A and B are in contact are frictionless. However, these surfaces have a coefficient of static friction, so a frictional force must act on block A. *The third is right bc the static frictional force that blocks A and B exert on each other has a magnitude f. The force that B exerts on A is directed to the right (the positive direction), while the force that A exerts on B is directed to the left. Blocks B and C also exert static frictional forces on each other, but these forces have a magnitude 2f, because the normal force pressing B and C together is twice the normal force pressing A and B together. The force that C exerts on B is directed to the right, while the force that B exerts on C is directed to the left. In summary, then, block A experiences a single frictional force +f, which is the net frictional force; block B experiences two frictional forces, -f and +2f, the net frictional force being -f +2f = +f; block C experiences a single frictional force +2f, which is the net frictional force. It follows that fs,A = fs,B = fs,C/2. **the second to last is wrong bc it states that the net frictional force acting on block C is zero, which implies that the surfaces where blocks B and C are in contact are frictionless. However, these surfaces have a coefficient of static friction, so a frictional force must act on block C. **the last one is incorrect bc it states that the net frictional forces acting on blocks A and C have the same magnitude. However, a greater frictional force acts on block C than on block A, because the normal force pressing blocks B and C together is greater than the normal force pressing blocks A and B together.

10) Three boys of equal strength try to break a rope (and fail) by tying one end to a fence post and tugging on the other end. Three additional boys (about the same strength as the others) come along and offer their assistance. Which of the following will maximize the tension in the rope? -Keep one end of the rope tied to the post and have all six boys tug on the other end. -Untie the rope from the post and have three boys tug on one end and the remaining three on the other (like a tug-of-war). -It does not matter: the rope sustains the same tension in both cases.

--Keep one end of the rope tied to the post and have all six boys tug on the other end. **Tension is the force which is present in a stringent/rope/chain etc, it is produced in the object when's force is applied on the object. It makes the rope to hold the force In the case above maximum tension will be applied by the rope when maximum force is applied on the rope i.e."keep one end of the rope tied to the post and have all six boys tug on the other end" Because by Newton's 3rd law for every action there is an equal and opposite reaction" .when six boys tug on one end the post also will apply force equal to that of those six boys. Hence the rope experience maximum tension

11) Each drawing shows three points along the path of a projectile, one on its way up, one at the top, and one on its way down. The launch point is on the left in each drawing. Which drawing correctly represents the acceleration a of the projectile at these three points?

-4 **The acceleration of a projectile is the same at all points on the trajectory. It points downward, toward the earth, and has a magnitude of 9.80 m/s2.

1) An object is moving at a constant velocity. All but one of the following statements could be true. Which one cannot be true? -No forces act on the object. -Three forces act simultaneously on the object. -A single force acts on the object. -Two forces act simultaneously on the object.

-A single force acts on the object. **If only one force acts on the object, it is the net force; thus, the net force must be nonzero. Consequently, the velocity would change, according to Newton's first law, and could not be constant. **This statement could be true if the two forces had equal magnitudes and exactly opposite directions. Then the net force would be zero, and the velocity would remain constant, according to Newton's first law.

5a Two particles are located on the -axis as shown. Particle 1 has a mass , and particle 2 has a mass of . Where on the -axis, as indicated by the letters A, B, C, and D, is closest to the center of mass of this system?

-B 3m is heavier

2a) Which of the following statements about centripetal acceleration is true? I. An object moving with a constant velocity cannot have a centripetal acceleration. II. An object moving with a constant speed may have a centripetal acceleration.

-Both 1 and 2 **An object experiencing a centripetal acceleration must be moving along a circular path. Therefore, the velocity vector is constantly changing direction.

10) Two balls are thrown from the top of a building, as in the drawing. Ball 1 is thrown straight down, and ball 2 is thrown with the same speed, but upward at an angle θ with respect to the horizontal. Consider the motion of the balls after they are released. Which one of the following statements is true? -Ball 2 has an acceleration in both the horizontal and vertical directions, but Ball 1 has an acceleration only in the vertical direction. -The acceleration of Ball 2 decreases as it rises, becomes zero at the top of the trajectory, and then increases as the ball begins to fall toward the ground. -Both balls have the same acceleration at all times. -The acceleration of Ball 1 becomes larger and larger as it falls, because the ball is going faster and faster.

-Both balls have the same acceleration at all times. (nothing is pushing or pulling either in the x axis, but both do have acceleration in the y bc of gravity) **Neither ball has an acceleration in the horizontal direction (ax = 0 m/s^2).

5b -Note that all of the kinematic equations contain the initial velocity, Vo. If a problem gives you three kinematic variables that do not including Vo, and you are asked to find a variable other than , how should you proceed? -The problem statement must be incomplete. -There is no procedure, the problem is not solvable. -There must be implied information that was missed. -First, use the three given variables to obtain , and then use a second equation to find the unknown variable asked for in the problem.

-First, use the three given variables to obtain , and then use a second equation to find the unknown variable asked for in the problem.

1) A jogger runs along a straight and level road for a distance of 8.0 km and then runs back to her starting point. The time for this roundtrip is 2.0 h. Which one of the following is true? -Her average speed is 8.0 km/h, but there is not enough information to determine her average velocity. -Her average speed is 8.0 km/h, and her average velocity is 8.0 km/h. -Her average speed is 8.0 km/h, and her average velocity is 0 km/h.

-Her average speed is 8.0 km/h, and her average velocity is 0 km/h.

5a) Which of the following statements is true? -Newton's third law is also known as the action/reaction law. -Newton's third law is only valid for contact forces. -Newton's third law states that for every acceleration of one object, there is an equal but opposite acceleration of another object. -Newton's third law is also known as F=ma

-Newton's third law is also known as the action/reaction law.

13) Which one of the following is true, according to Newton's laws of motion? Ignore friction. -A sports utility vehicle (SUV) hits a stationary motorcycle. Since it is stationary, the motorcycle sustains a greater force than the SUV does. -A semitrailer truck crashes all the way through a wall. Since the wall collapses, the wall sustains a greater force than the truck does. -Sam (18 years old) and his sister (9 years old) go ice skating. They push off against each other and fly apart. Sam flies off with the greater acceleration. -Two astronauts on a space walk are throwing a ball back and forth between each other. In this game of catch the distance between them remains constant. -None of the these is true, according to the third law.

-None of the these is true, according to the third law. *The third one is false bc According to the third law, Sam and his sister experience forces of equal magnitudes during the push-off. Since Sam has the greater mass, he flies off with the smaller acceleration, according to the second law. *The fourth one is false bc in catching and throwing the ball each astronaut applies a force to it, and, according to the third law, the ball applies an oppositely directed force of equal magnitude to each astronaut. These reaction forces accelerate the astronauts away from each other, so that the distance between them increases. **Answers (a) and (b) are false, according to the third law, which states that whenever one body exerts a force on a second body, the second body exerts an oppositely directed force of equal magnitude on the first body. It does not matter whether one of the bodies is stationary or whether it collapses. Answer (c) is false because, according to the third law, Sam and his sister experience forces of equal magnitudes during the push-off. Since Sam has the greater mass, he flies off with the smaller acceleration, according to the second law. Answer (d) is false because in catching and throwing the ball each astronaut applies a force to it, and, according to the third law, the ball applies an oppositely directed force of equal magnitude to each astronaut. These reaction forces accelerate the astronauts away from each other, so that the distance between them increases.

6) Two objects A and B accelerate from rest with the same constant acceleration. Object A accelerates for twice as much time as object B, however. Which one of the following statements is true concerning these objects at the end of their respective periods of acceleration? Object A will be moving eight times faster than object B. -Object A will travel four times as far as object B. -Object A will travel twice as far as object B. -Object A will travel eight times further than object B. -Object A will be moving four times faster than object B.

-Object A will travel four times as far as object B.

6a -You and a friend are standing on the edge of a cliff of height . You throw a ball straight upward at the same time your friend throws a ball straight downward, off the edge. You both throw with the same initial speed, . Assuming the ball projected upward misses the edge of the cliff on the way down, which ball will hit the ground first, and which one will hit with the greater velocity? -The ball project downward will hit first, but the two will hit with equal velocities. -The ball projected downward will hit first and with the greatest velocity. -The ball projected upward reverses course, catches up and passes the ball initially projected downward, and hits the ground first, and with the greatest velocity.

-The ball project downward will hit first, but the two will hit with equal velocities.

6b) Considering that there are only three fundamental forces in nature from which all other forces can be derived, which of the three are responsible for the forces between atoms that hold solid materials together? -It is the gravitational attraction (the gravitational force) between the atoms. -The electroweak force because the bonding in materials is carried out by electrons (electric charges). -It is the nuclear strong force between the nucleons in the nuclei of the atoms.

-The electroweak force because the bonding in materials is carried out by electrons (electric charges).

8a) A square, four-legged table with a weight of 400 N rests on an even concrete floor. Assuming the weight is evenly distributed, what is the direction and magnitude of the normal force between the floor and each foot of the table? -The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N. -The floor provides a force vertically upward (perpendicular to the floor) on each leg with a magnitude of 400 N. -The floor provides a normal force parallel to the floor on each leg with a magnitude of 100 N. -The floor provides a force parallel to the floor on each leg with a magnitude of 400 N.

-The floor provides a normal force vertically upward (perpendicular to the floor) on each leg with a magnitude of 100 N.

5a) -The phrase "it starts from rest" appears in statement of a kinematics problem regarding the motion of an object. What can you infer from this statement? -The final velocity of the object is zero. -The initial velocity of the object is zero. -The acceleration of the object is negative. -None of the above.

-The initial velocity of the object is zero.

4b) Consider two identical frictionless and banked curves - one is located on the earth, and the other is on the moon. If identical cars are to travel around each curve along a circle of the same radius, how must the speeds of the two cars compare? The speeds of the two cars must be the same. The speed of the car on the moon must be greater than the speed of the car on the earth. The speed of the car on the earth must be greater than the speed of the car on the moon.

-The speed of the car on the earth must be greater than the speed of the car on the moon. **Equation 5.4 shows the relationship between the bank angle, the car's speed, and the radius of the circular motion. Furthermore, notice that this relationship also depends on the value of , which will be different on the earth and the moon.

5a)A satellite is in a circular orbit around a planet. A second satellite is placed in a different circular orbit that is farther away from the same planet. How do the speeds of the two satellites compare? -The speeds of the two satellites are equal. -The speed of the second satellite is less than the speed of the first satellite. -The speed of the second satellite is greater than the speed of the first satellite.

-The speed of the second satellite is less than the speed of the first satellite. **look at the equation. Smaller r means that you need to increase speed to maintain that orbit

4b Object 1 is moving in the positive -direction. It collides with a second object that is initially at rest. The collision is not head-on, so the objects move off in different directions after the collision (see figure). What must be true about the total momentum of object 1 and object 2 in the -direction after the collision? -The total momentum in the -direction after the collision will be equal to zero. -The total momentum in the -direction after the collision will point in the negative -direction, because object 1 has a greater speed after the collision. -The total momentum in the -direction after the collision will point in the positive -direction, because object 2 has a greater mass.

-The total momentum in the -direction after the collision will be equal to zero. **not the second or third bc; The total momentum must be conserved separately in both the - and -direction. Since the total momentum in the -direction is equal to zero before the collision, the total momentum in the -direction after the collision must also be equal to zero.

11b) In which one of the following situations could an object possibly be in equilibrium? -Three forces act on a single object. The forces all point along the same line, but may have different directions. -Two perpendicular forces act on an object. -A single force acts on an object. -None of the above.

-Three forces act on a single object. The forces all point along the same line, but may have different directions. **When two non-zero forces act perpendicular to a body, the net resultant cannot be equal to zero for those two forces. 2 For a body to be in an equilibrium, the forces must be indivisually zero in two mutually perpendicular directions. 3 For a force to be zero in any single direction, there must atleast be two forces in each direction. 4 Using the above rules, in option a, the net forces can be possibly zero in this case.

18 A nonzero net force acts on a particle and does work. Which one of the following statements is true? -The kinetic energy, speed, and velocity of the particle change. -The kinetic energy and the speed of the particle change, but the velocity of the particle does not change. -The kinetic energy of the particle changes, but the speed of the particle does not change. -The kinetic energy of the particle changes, but the velocity of the particle does not change. -The kinetic energy of the particle does not change, but the speed of the particle does change.

-first *The work-energy theorem states that W = KEf - KE0. Since work is done, the kinetic energy changes. Since kinetic energy is , the speed v must also change. Since the instantaneous speed is the magnitude of the instantaneous velocity, the velocity must also change.

7b) You and your friends are riding a rollercoaster. You enter a vertical loop-the-loop, turn upside-down, and then come out again at the bottom of the loop. This is similar to what the motorcycle stuntman did in the video. As you pass through the very bottom of the loop, do you feel heavier or lighter than normal? -You feel lighter. -You feel normal, just as if you were sitting at rest at your desk. -You feel heavier.

-heavier

3 You are in a tall building located near the equator. As you ride an elevator from the ground floor to the top floor, your tangential speed due to the earth's rotation ____________. does not change decreases increases when the speed of the elevator increases and decreases when the speed of the elevator decreases increases

-increases *you need to Consider how the tangential speed depends on the radius of the rotational motion *its not the third bc; The tangential speed is the magnitude of the tangential velocity, which is tangent to the earth's surface. The speed of the elevator is the magnitude of the elevator's velocity, which is perpendicular to the earth's surface. The two speeds are not related in any way. Consider how the tangential speed depends on the radius of the rotational motion.. **the correct one is right bc according to (vT = rω), the tangential speed is proportional to the radius r when the angular speed ωis constant, as it is for the earth. As the elevator rises, the radius, which is your distance from the center of the earth, increases, and so does your tangential speed.

2a You are a passenger on a jetliner that is flying at constant velocity. You get up from your seat and walk toward the front of the plane. Because of this action, your forward momentum increases. What happens to the forward momentum of the plane itself? It decreases. It increases. It remains constant.

-it decreases **it is not the last bc; The passenger and the plane constitute the system. They only interact via internal forces, therefore, the total momentum must be conserved.

1a A cable applies a vertical force to a crate with a mass of 70.0 kg. It first lifts the crate to a height of 12.0 m above the floor, and then lowers it back to the floor. What is the total work done by the force?

0 (started and finished at same spot)

4 A pitcher throws a curveball that reaches the catcher in 0.68 s. The ball curves because it is spinning at an average angular velocity of 250 rev/min (assumed constant) on its way to the catcher's mitt. What is the angular displacement of the baseball (in radians) as it travels from the pitcher to the catcher?

17.802 rad

3b Staring from rest, a lawn mower blade undergoes a constant acceleration of 125.0 rad/s^2. How many revolutions does it undergo in 2.0 s? 20 rev 250 rev 40 rev 80 rev

40 rev

2 A rotating object has an angular acceleration α that is not zero. Which one or more of the following three statements is consistent with a non-zero angular acceleration? A. The angular velocity ω increases as time passes. B. The angular velocity ω has the same value at all times. C. The angular velocity ω decreases as time passes. A and C, but not B A and B, but not C A, B, and C A only B and C, but not A

A and C, but not B

6a A ball starts with an initial kinetic energy of 1000 J and zero gravitational energy potential. At some later time, the ball has zero kinetic energy and 1150 J of gravitational potential energy. Which of the following is true? A nonconservative force does positive work on the ball. A nonconservative force does negative work on the ball. There are no nonconservative forces acting on the ball.

A nonconservative force does positive work on the ball.

3b) In Case A, an object is moving in a straight line at a constant speed of 9.8 m/s. In Case B, an object is moving in a straight line with a constant acceleration of 9.8 m/s2. Which of the following statements is true? A nonzero net external force acts on the object in Case A only. A nonzero net external force acts on the object in Case B only. A nonzero net external force acts on the object in both cases. A nonzero net external force acts on the object in neither case.

A nonzero net external force acts on the object in Case B only.

1 A rotating object has an angular acceleration of α = 0 rad/s2. Which one or more of the following three statements is consistent with a zero angular acceleration? A. The angular velocity is ω = 0 rad/s at all times. B. The angular velocity is ω = 10 rad/s at all times. C. The angular displacement θ has the same value at all times. B only A, B, and C A only A and B, but not C C only

A, B, and C **An angular acceleration of zero means that the angular velocity has the same value at all times, as in statements A or B. However, statement C is also consistent with a zero angular acceleration, because if the angular displacement does not change as time passes, then the angular velocity remains constant at a value of 0 rad/s.

9b) A box is at rest on the floor of an elevator. Because of static friction, a force is required to start the box sliding across the elevator floor. Compare the size of the pushing force required to move the box, when the elevator is (a) stationary, (b) accelerating upward, and (c) accelerating downward. Rank these forces from smallest to largest. Accelerating upward, stationary, accelerating downward Accelerating downward, stationary, accelerating upward Stationary, accelerating upward, accelerating downward Stationary, accelerating downward, accelerating upward

Accelerating downward, stationary, accelerating upward

8a A stone is projected at a 45° above the horizontal. At the peak of its trajectory, what types of energy does it possess? Kinetic Gravitational potential Thermal Energy due to its mass () All of the above

All of the above

4b A ball is dropped vertically from a height h. When it rebounds from the floor it attains a maximum height of 2/3 h . What statement is true?

As the hight is decreased the potential energy is decreased too, so there is a non conservative force and then there is also a gain in the energy as it is bouncing back so both the conservative and non conservative forces are acts on the ball

24) Three identical blocks are being pulled or pushed across a horizontal surface by a force F, as shown in the drawings. The force F in each case has the same magnitude. Rank the kinetic frictional forces that act on the blocks in ascending order (smallest first).

B, A C **The magnitude of the kinetic frictional force is proportional to the magnitude of the normal force. The normal force is smallest in B, because the vertical component of compensates for part of the block's weight. In contrast, the normal force is greatest in C, because the vertical component of adds to the weight of the block.

25) A heavy block is suspended from a ceiling using pulleys in three different ways, as shown in the drawings. Rank the tension in the rope that passes over the pulleys in ascending order (smallest first).

B, C, A **In B the tension T is the smallest, because three rope segments support the weight W of the block, with the result that 3T = W, or T = W/3. In A the tension is the greatest, because only one rope segment supports the weight of the block, with the result that T = W.

7a) A body is moved from sea level to the top of a high mountain. Which of the following statements is/are true concerning the following quantities? I. The body's mass. II. The body's weight .III. The gravitational force on the body. Both II and III change. Both I and III change. Only III changes. Only I changes. Only II changes.

Both II and III change.

3b Which of the letters below most closely matches the location of the center of gravity of the baseball bat?

C

A flywheel with mass 120 kg, and radius 0.6 m, starting at rest, has an angular acceleration of 0.1 rad/s2. How many revolutions has the wheel undergone after 10 s? Which formula should the student use to answer the question? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a A b B c C d None of the above

C

A ladybug is clinging to the rim of a spinning wheel which is spinning CCW very fast and is slowing down. At the moment shown, what is the approximate direction of the ladybug's acceleration? HINT: Remember that acceleration has two components, so the resultant is what I am asking for in here. Make a drawing ! Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a A b B c C d D e None of the above

C

5b The figure below shows the top view of two balls colliding on a horizontal frictionless table. The path followed by the center of mass of this system is shown by the black vector. Which path, labeled A, B, C, or D, will the center of mass follow after the collision?

C *Since momentum is conserved in the collision, the velocity of the center of mass is the same both before and after the collision.

Two cars are traveling at the same constant speed v. Car A is moving along a straight section of the road, while B is rounding a circular turn. Which statement is true about the acceleration of the cars? Both cars are accelerating. Car A is accelerating, but car B is not accelerating. The acceleration of both cars is zero, since they are traveling at a constant speed. Car A is not accelerating, but car B is accelerating.

Car A is not accelerating, but car B is accelerating.

3a True or False: In an elastic collision, the kinetic energy of each object is the same both before and after the collision. True False

False **It is the total kinetic energy of the system that is the same both before and after the collision.

6a) True or False? When an astronaut is in orbit around the earth, she is weightless? False True

False--what is happening is their apparent weight is 0 due to the space station being in a freewill towards earth (like elevator freefall example) which is why they float, but their mass is unchanged

5b) A father and his seven-year-old daughter are facing each other on ice skates. With their hands, they push off against one another. Which of the following statements is/are true? I. Each experiences an acceleration that has a different magnitude. II. Each experiences an acceleration that has the same magnitude. III. Each experiences a pushing force that has a different magnitude. IV. Each experiences a pushing force that has the same magnitude. I and IV only II and IV only I and III only II and III only

I and IV **When the daughter pushes her father with some force, same amount of force is exerted on her (Newton's third law). So, they experience same amount of force. Since the forces are same but the masses to the two are different, they experience acceleration which has different mangnitude.

1a Two objects have the same momentum. Which of the following is true? I. The masses of the objects are equal .II. The speeds of the objects are equal. III. The velocities of the objects are equal. IV. The direction of motion of each object is the same. I only II and IV II only IV only II and III I and II III only

IV only p=mv

You are trying to open a door that is stuck by pulling on the doorknob in a direction perpendicular to the door. If you instead tie a rope to the doorknob and then pull with the same force, is the torque you exert increased? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Yes b No

No

5b) Which of the following statements is correct concerning satellites in orbit around the same planet? The period of a satellite depends on its mass. Satellites located closer to the planet have longer periods. The period of a satellite is independent of the planet's mass. If the orbital radius of a satellite doubles, then its period increases by a factor of 4. None of the above statements are correct.

None of the above statements are correct.

7b) Three particles have identical masses. Each particle experiences only the gravitational forces from the other two particles. How should the particles be arranged so that each one experiences a net gravitational force of the same magnitude? Equally spaced on a straight line. On the corners of a right triangle. On three of the four corners of a square. Three particles have identical masses. Each particle experiences only the gravitational forces from the other two particles. How should the particles be arranged so that each one experiences a net gravitational force of the same magnitude? Equally spaced on a straight line. On the corners of a right triangle. On three of the four corners of a square. On the corners of an equilateral triangle.

On the corners of an equilateral triangle. **Remember, the net gravitational force (always attractive) on a particle will be equal to the vector sum of the forces from all the other particles (here, the other two).

5b A ball hangs on the end of a string that is connected to the ceiling so that it swings like a pendulum. You pull the ball up so that it nearly touches the end of your nose. You let the ball swing down (from rest), and then swing back, toward your face. Under which conditions will the ball strike your nose? Only if energy is somehow added to the ball. When only gravity acts on the ball. When gravity and air friction act on the ball.

Only if energy is somehow added to the ball.

2b A uniform ladder is at rest leaning against a smooth wall (frictionless) as shown in the figure at the left. The base of the ladder is on rough ground (friction). The corresponding free-body diagram for the ladder is shown in the figure at the right. Which of the following must be true? The sum of the forces in the x-direction must be equal to zero. The sum of the forces in the y-direction must be equal to zero. The sum of the torques acting on the ladder must be equal to zero. All of the above must be true.

Since the ladder is in equilibrium, the net force and net torque on it must be equal to zero. Thus the correct option is all

1a) Suppose you drive 1500 m due east in 2 minutes. You then turn due north and drive the same distance in the same time. Which of the following is true concerning the average speeds and average velocities for each segment of your trip? The average speeds are the same, and the average velocities are the same. The average speeds are different, but the average velocities are the same. The average speeds are different, and the average velocities are different. The average speeds are the same, but the average velocities are different.

The average speeds are the same, but the average velocities are different. **velocity is a vector, so has a mag and direct!

19 A ball is fixed to the end of a string, which is attached to the ceiling at point P. As the drawing shows, the ball is projected downward at A with the launch speed v0. Traveling on a circular path, the ball comes to a halt at point B. What enables the ball to reach point B, which is above point A? Ignore friction and air resistance. The ball's initial gravitational potential energy. The work done by the tension in the string. The ball's initial kinetic energy. The work done by the gravitational force.

The ball's initial kinetic energy. first is wrong bc; The final position of the ball at B is above its initial position. Therefore, the final potential energy is greater than the initial potential energy. As a result, the initial potential energy cannot supply the energy to enable the ball to rise above its initial vertical level. The necessary energy must come from some other supply of energy.

14) A tennis ball is thrown upward at an angle from point A. It follows a parabolic trajectory and hits the ground at point D. At the instant shown, the ball is at point B. Point C represents the highest position of the ball above the ground. Which statement is true concerning the ball when it is at C, the highest point in its trajectory? The ball's velocity is zero, but its acceleration is not zero. The ball's velocity is perpendicular to its acceleration. The ball's velocity is not zero, but its acceleration is zero. The ball's velocity and acceleration are both zero. The horizontal and vertical components of the ball's velocity are equal.

The ball's velocity is perpendicular to its acceleration. **The ball's velocity is zero, but its acceleration is not zero. This is wrong bc although at the max point the velocity of Y is 0, the velocity of X is not ). If it was then it would just drop straight down

3a What is the point at which the weight of rigid object can be considered to act when producing a torque on the object? The center of force. The center of inertia. The center of gravity. The center of torque.

The center of gravity.

16 The same force F pushes in three different ways on a box moving with a velocity v, as the drawings show. Rank the work done by the force F in ascending order (smallest first). C, A, B A, C, B B, A, C C, B, A A, B, C

The first! *3rd is wrong. This answer says that the maximum work is done in C. However, in A and B positive work is done, since the force has a component in the direction of the displacement in each case. Furthermore, when the force is perpendicular to the displacement, as in C, there is no work. Thus, C cannot correspond to the maximum work. 4th is wrong: This answer says that there is more work in A than in B. However, in A only a component of the force points in the direction of the displacement, whereas in B the entire force points in the direction of the displacement. Thus, the work done in A cannot be greater than the work done in B.

A 3830 kg demolition ball swings at the end of a 22.9 m cable on the arc of a vertical circle. At the lowest point of the swing, the ball is moving at a speed of 1.87 m/s. Determine the tension in the cable.

The skier at A is speeding up, so the direction of the acceleration, and hence the net force, must be parallel to the skier's velocity. At B the skier is momentarily traveling at a constant speed on a circular path of radius r. The direction of the net force, called the centripetal force, must be toward the center of the path. At C the skier is in free-fall, so the net force, which is the gravitational force, is straight downward.

6b) A rotating space station creates artificial earth-like gravity. If the size of the space station is enlarged, such that its radius increases by a factor of 4, what must happen to the speed of the station floor, so that the artificial earth-like gravity is maintained? The speed of the station floor should increase by a factor of 4. The speed of the station floor should decrease by a factor of 2. The speed of the station floor should increase by a factor of 2. The speed of the station floor should remain constant. The speed of the station floor should decrease by a factor of 4.

The speed of the station floor should increase by a factor of 2. **remember equation, V=sqrt(g)(r). We can rearrange this to g=v^2/r. If the radius of the station is increased by a. factor of 4 that would make our equation g = v^2/4r. If velocity is doubled then g = (2v)^2/4r which = v^2/r so that's the same thing.

11a) A stone is thrown from the top of a high cliff. Air resistance is negligible. As the stone falls, which of the following is true? The stone is in equilibrium during the first half of its fall and then nonequilibrium for the second half. The stone is never in equilibrium as it falls. The stone is in equilibrium continuously as it falls.

The stone is never in equilibrium as it falls. **The forces must be zero in two perpendicular directions in two dimension. In the case of throwing an object under the influence of gravity, the gravitational forces are always acting on the object and it is the only force acting on it since the air resistance is absent. Since there is always a non-zero force in the vertical direction on the body of stone, so it is not in equilibrium.

3b A car of mass moving with a speed collides with an identical car that is at rest. After the collision, the cars stick together. Which of the following statements is false? The speed of the cars after the collision is . This collision is completely inelastic. The total kinetic energy before and after the collision is conserved. The total momentum before and after the collision is conserved.

The total kinetic energy before and after the collision is conserved.

Two balls begin at rest at the same height (but not at the same place). At time t=0, one of them (A) is simply released, and the other one (B) is launched straight horizontally. (After t=0, both of them are then freely falling.) Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a (A) hits the ground first b (B) hits the ground first c They both hit the ground simultaneously d Depends on which one is heavier

They both hit the ground simultaneously Explanation You can consider horizontal and vertical motion separately, in the absence of friction. In the vertical direction, both start with v0y= 0, and must travel the same distance. They will hit at the same time.

6b) Vectors A,B and C satisfy the following equation A + B = C and their magnitudes are related by the scalar equation A+ B = C . How is A vector oriented with respect to B vector ? Vectors A and B are collinear and point in opposite directions. Vectors A and B are collinear and point in the same direction. Vectors A and B can only be equal to zero. Vectors A and B are perpendicular to each other. There is no way to tell the orientation of vectors and from the given information.

Vectors A and B are collinear and point in the same direction. (the addition tells us this)

The Hubble Space telescope is orbiting earth (uniform circular motion) at a height of 598 km above earth's surface. It has detected the light being emitted from many galaxies that are very very far away ! But, what do you think keeps the telescope in orbit? That is, what force provides the centripetal acceleration? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Gravitational Force b Normal Force c Static Frictional Force d Kinetic Frictional Force

aGravitational Force

If you drop an object in the absence of air resistance, it accelerates downward at 9.8 m/s^2. If instead you throw it downward, its downward acceleration after release is Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a less than 9.8 m/s^2 b 9.8 m/s^2 c more than 9.8 m/s^2 d none of the above

b 9.8 m/s^2

You are a passenger in a car and not wearing your seat belt. Without increasing or decreasing its speed, the car makes a sharp left turn, and you find yourself colliding with the right-hand door. Which is the correct analysis of the situation? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a During the turn, there is a rightward force pushing you into the door b During the turn, the door exerts a leftward force on you. c both of the above d neither of the above

b During the turn, the door exerts a leftward force on you.

A car moves at a constant speed along a straight line as it approaches a circular turn. In which of the following parts of the motion is the car not in equilibrium? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a As it moves along a straight line towards the circular turn b as it is going around the turn c As it moves away from the turn along a straight line

b as it is going around the turn

A small wheel and a large wheel are connected by a belt. The small wheel is turned at a constant angular velocity. How does the magnitude of the angular velocity of the large wheel compare to that of the small wheel? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a omega (s) = omega (L) b omega (s) > omega (L) c omega (s) < omega (L)

bomega (s) > omega (L)

An ant crawling along the floor follows a semi-circular path, going half way around the circumference of a circle of radius R. The distance traveled, and the displacement of the ant, are respectively: Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a πR and πR b 2R and πR c πR and 2R d πR and 0 e none of these

c πR and 2R

An astronaut floating weightlessly in orbit shakes a large iron anvil rapidly back and forth. She reports back to Earth that Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a the shaking costs her no effort because the anvil has no inertial mass in space. b the shaking costs her some effort but considerably less than on Earth. c although weightless, the inertial mass of the anvil is the same as on Earth.

c although weightless, the inertial mass of the anvil is the same as on Earth.

A compact car and a large truck collide head on and stick together. Which vehicle undergoes the larger acceleration during the collision? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a car b truck c Both experience the same acceleration. d Can't tell without knowing the initial velocities.

car

3b A stone is thrown horizontally from the top of a cliff and eventually hits the ground below. A second stone is dropped from rest from the same cliff, falls through the same height, and also hits the ground below. Consider the three quantities below. Are they the same for the two stones, or different? a) Displacement (b) Speed just before impact with the ground (c) Time of flight

different Since the initial speed of each projectile is zero in the vertical direction, they will fall the same height in the same time. However, the first stone has an initial velocity in the horizontal direction. It will, therefore, travel a greater total distance than the dropped stone, and hit the ground with a greater speed. different (the first has a velocity in the x and y and since C^2 = A^2 + B^2 same (they have the same y) Since the initial speed of each projectile is zero in the vertical direction, they will fall the same height in the same time. However, the first stone has an initial velocity in the horizontal direction. It will, therefore, travel a greater total distance than the dropped stone, and hit the ground with a greater speed.

14 A high-jumper, having just cleared the bar, lands on an air mattress and comes to rest. Had she landed directly on the hard ground, her stopping time would have been much shorter. Using the impulse-momentum theorem as your guide, determine which one of the following statements is correct. The air mattress exerts a smaller impulse, and a smaller net average force, on the high-jumper than does the hard ground. The air mattress exerts a greater impulse, but a smaller net average force, on the high-jumper than does the hard ground. The air mattress exerts a greater impulse, and a greater net average force, on the high-jumper than does the hard ground. The air mattress exerts the same impulse, but a greater net average force, on the high-jumper than does the hard ground. The air mattress exerts the same impulse, but a smaller net average force, on the high-jumper than does the hard ground.

last one **1.The impulse must be the same because the same falling motion has to be stopped.2.The net avg force is smaller because the collision between the bag and the jumper has a larger time than the jumper and the ground so the average force experienced by the jumper is less during the bad collision. **According to the impulse-momentum theorem, the impulse is equal to the final momentum minus the initial momentum. Therefore, the impulses are the same in both cases, since the final momenta are the same and the initial momenta are the same. The impulse is also the product of the net average force and the time of impact. Since the impulses are equal and the time of impact is larger for the air mattress than for the ground, the air mattress exerts a smaller net average force on the high jumper.

6a) Can two nonzero perpendicular vectors be added together so their sum is equal to zero?

no

A hockey puck slides without friction along a frozen lake toward an ice ramp and plateau as shown. The speed of the puck is 4m/s and the height of the plateau is 1m. Will the puck make it all the way up the ramp? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a yes b no c impossible to determine without knowing the mass of the puck

no

There is a bug S on the rim of the small wheel and another bug L on the rim of the large wheel. How do their speeds compare? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a S = L b S > L c S < L

s = L

A compact car and a large truck collide head on and stick together. Which undergoes the larger momentum change? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a car b truck c The momentum change is the same for both vehicles. d Can't tell without knowing the initial velocities.

same for both

4a A skateboarder wants to cross a large playground and notices that there are large shapes painted on its asphalt surface. One shape is a large circle that covers the entire playground. Inscribed in that circle is a square, with one point at the skateboarder's feet and the other at his destination. The surface is rough and, therefore, friction is present. What path does he follow in order to minimize the work done by nonconservative forces? The circle. The path does not matter. The square.

square He must travel the least distance to minimize the work done by non conservative forces.

Which of the two friction forces is responsible for propelling you forward as you walk? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a Kinetic Friction b Static Friction c both forces d neither

static friction

A ball bounces off the floor as shown. The direction of the impulse on the ball, Δp, is Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a straight up ↑ b straight down ↓ c to the right → d to the left ←

straight up

A ball is thrown straight up. At the top of its trajectory, its Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a velocity is zero, accel. is zero b velocity is non-zero, accel. is non-zero c velocity is zero, accel. is non-zero d velocity is non-zero, accel. is zero

velocity is zero, accel. is non-zero