physics 221 test 1

A driver in a car accelerating towards the right has an apparent weight with components 939 N pointing down and 649 N pointing towards the left. What is the magnitude of the acceleration of the car in m/s2? Enter a number with 1 digit after the decimal point. Let g = 9.8 m/s2.

6.8

A 1200 kg car's speed changes from 0 to 20 m/s in 4 s. What is the average power of the car motor during this time period? Neglect friction. 60 kW 3 kW 24 kW 12 kW 1200 W

60 kW

A 1400 kg car accelerates uniformly from rest to 60 mph in 6 s. Find the net force needed to produce this motion. 84000 N 14000 N 6259 N 233 N 1400 N

6259 N

The magnitude of the force vector with (x, y) components (5 N, 5 N) is 10 N. zero. 7.1 N. 5 N. 8.3 N.

7.1 N

A person weighing 1103 N stands in an elevator that decelerates at a rate of 1.9 m/s2 while moving upward. What is the magnitude of the force in N exerted on the person by the floor of the elevator while it is decelerating? Use g = 9.8 m/s2. Enter an integer. Round up or down correctly.

889

A rock is thrown vertically into the air. At the very top of its trajectory, its velocity is momentarily zero. What is its acceleration at this point? Zero 9.8 m/s2 greater than 0 but less than 9.8m/s2

9.8 m/s^2

An object's velocity in the positive x-direction changes from 4.2 m/s to 12.8 m/s in 4.7 s. A force of constant magnitude 18 N is acting on it. What is the object's mass in kg? Enter a number with two digits behind the decimal point.

9.84

Two children pull a sled as shown. The sled moves with constant velocity v. Find the frictional force on the sled. 90.6 N 50 N 45 N 42 N 0

90.6 N

A particle is moving with constant speed along the circular path shown. Its velocity vector is shown at two different positions. What is the direction of the acceleration when the particle is at point X?

A (west)

A car's speed changes from 20 mph to 60 mph. By what factor does its kinetic energy change? There is no way to tell. It will increase by a factor of 3. It will increase by a factor of 6. It will increase by a factor of 9. It will stay constant.

It will increase by a factor of 9.

A clever physics student is able to sneak a scale on a popular ride at an amusement park. Before the ride begins to move, the scale reads 700 N for the student's weight. As the ride lifts, it initially accelerates upward at 3 m/s2. At the top, the riders are held in suspense before the gondola is allowed to free fall downward with acceleration equal to g. What should the scale read for the student's apparent weight during the lift and the fall? Lift: 2100 N, Fall: 700 N Lift: 490 N, Fall: 1400 N Lift: 910N, Fall: 0 N Lift: 490 N, Fall: 0 N Lift: 910 N, Fall: 700 N

Lift: 910N, Fall: 0N

In an inertial frame, an object cannot remain at rest unless which of the following holds? The net force acting on it is zero. There are no forces at all acting on it. The net force acting on it is constant. There is only one force acting on it.

The net force acting on it is zero

A 10 kg and a 4 kg mass are acted on by the same magnitude net force (which remains constant) for the same period of time. Both masses are at rest before the force is applied. After this time, the 10 kg mass moves with a speed v1 and the 4 kg mass moves with a speed v2. Which of the following is true? The ratio v1/v2 is equal to 5/2 v1 is equal to v2 The ratio v1/v2 is equal to (2/5)^2 The ratio v1/v2 is equal to 2/5

The ratio v1/v2 is equal to 2/5

Two pitchers are standing side by side, and simultaneously throw baseballs A and B. The balls follow the parabolic trajectories shown. Which of the following statements is true?

ball B (more stretched out line) hits the ground before ball A (more condensed line)

You drop an object from a bridge and simultaneously, you throw a-other object downwards at 10 m/s. As the objects are falling, which object has the larger acceleration? (Ignore air resistance.) The dropped object. The thrown object. Both objects have the same acceleration. It depends on the masses of the objects.

both objects have the same acceleration

Consider motion in one dimension. (The sign of the vector quantities is their direction indicator.) An object moves in the positive x-direction with speed 1.5 m/s for 2.7 s. It stops for 1.1 s and then accelerates with acceleration -5.4 m/s2 for 2.8 s. What is the average velocity of this object in units of m/s? Enter a number with two digits behind the decimal point.

-2.59

A boy holds a 40 N weight at arm's length for 10 s. His arm is 1.5 m above the ground. The work done by the force of the boy on the weight while he is holding it is 0. 60 J. 4 J. 6 J. 90 J.

0

Two cylindrical artificial bones are made of the same material and length, one with twice the radius as the other. When the two have the same tension force applied, the larger bone stretches by what factor compared to the smaller bone 4 2 1 0.5 0.25

0.25

Consider motion in one dimension. (The sign of the vector quantities is their direction indicator.) An object moves in the positive x-direction with speed 6.2 m/s for 1.3 s. It stops for 2.4 s and then moves in the negative x direction with speed 2.4 m/s for 2.6 s. What is the average velocity of this object in units of m/s? Enter a number with two digits behind the decimal point.

0.29

Another scheme to catch the roadrunner has failed and a safe falls from rest from the top of a 30.0 m high cliff toward Wile E. Coyote, who is standing at the base. Wile first notices the safe after it has fallen 15 m. How long does he have to get out of the way? 3.06 s 1.74 s 2.47 s 0.72 s 6.12 s

0.72 s

Which system is in a state of stable equilibrium? 1) A marble in the bottom of a spherical bowl 2) A marble on top of a spherical bowl 3) None of the above 4) A marble rolling down an inclined surface 5) A marble on a flat, level surface

1) A marble in the bottom of a spherical bowl

A rock is thrown straight up from the surface of the Earth. Which one of the following statements describes the energy transformation of the rock as it rises? Neglect air resistance. 1) The KE decreases and the PE increases. 2) Both the PE and the total energy of the rock increase. 3) The total energy of the rock increases. 4) Both the KE and the PE of the rock remain the same. 5) The KE increases and the PE decreases.

1) The KE decreases and the PE increases.

A force of 20 N in the positive x‐direction accelerates an object giving it a = 2 m/s2. When the object is moving with velocity v = 10 m/s, an additional force of 10 N in the negative x‐direction is applied. Which statement is true? 1) The object now accelerates with acceleration a = ‐1 m/s2 in the negative x‐direction. 2) The object now accelerates with acceleration a = 1 m/s2 in the positive x‐direction. 3) The object now moves with constant velocity. 4) The object slows down and comes to a stop.

1) The object now accelerates with acceleration a = 1 m/s2 in the positive x‐direction

Your class is rather unhappy with the instructor, and they pitch in and decide to fund a sabbatical for him to go to Mars. Unbeknownst to the students the following semester, the instructor has made long distance course arrangements so the "show can go on". The instructor begins talking about mass, weight and related things. He correctly makes which following statement: 1) his mass is still essentially unchanged but his weight is less than on earth. 2) his weight is still essentially unchanged but his mass is less than on earth. 3) his weight and mass have both decreased significantly. 4) his weight and mass have both increased significantly. 5) neither his weight nor his mass have changed much.

1) his mass is still essentially unchanged but his weight is less than on earth

A 969 kg car starts from rest. A constant force of 706 N acts on it. What is the distance (in m) it travels in 2 s? Enter a number with two digits behind the decimal point.

1.46

A car has a maximum acceleration of 4.5 m/s2. What would be its maximum acceleration while towing a second car twice its mass? 1. 2.25 m/s2 2. 2 m/s2 3. 1.5 m/s2 4. 1 m/s2 5. 0.5 m/s2

1.5 m/s^2

Two packages are dropped from an airplane. A parachute can increase the cross sectional area of each packages by a factor of 55. The parachute on package 1 fails to open, and the terminal speed of package 1 is 12 m/s. The parachute on package 2 opens. What is the terminal speed of package 2 in m/s? Enter a number with one digit after the decimal point.

1.6

As a bacterium swims through water it propels itself with its flagella so as to overcome the frictional drag forces and move at, more or less, constant velocity of 100 micrometer/s for periods of time. If the frictional drag force on a bacterium is 0.1 N, how much work does the bacterium do in 1 s? 10 microJoule 100 microJoule 100 milliJoule 1 J 1 milliJoule

10 microJoule

A person weighing 990 N stands in an elevator that decelerates at a rate of 1.3 m/s2 while moving downward. What is the magnitude of the force in N exerted on the person by the floor of the elevator while it is decelerating? Use g = 9.8 m/s2. Enter an integer. Round up or down correctly.

1121

A 2.8 kg object is brought to a stop from a speed of 1.1 m/s in 0.17 m by a spring system. What is the spring constant k of the spring? Enter an integer. Round up or down correctly.

117

A vector of magnitude 20 is added to a vector of magnitude 25. the magnitude of this sum might be 0 3 12 47 50

12

A Boeing 737 jet plane lands with a speed of 60 m/s (about 135 mi/h) and can decelerate on a wet runway at a maximum rate of 4 m/s2 as it comes to rest. What is the minimum time needed before the plane will come to rest? 2.25 s 4 s 12 s 35 s 15 s

15 s

Consider motion in one dimension. (The sign of the vector quantities is their direction indicator.) An object moves in the positive x-direction with speed 1.8 m/s for 2.4 s. It stops for 2.2 s and then moves in the negative x direction with speed 2.4 m/s for 4.6 s. What is the total distance traveled by the object in units of meter? Enter a number with two digits behind the decimal point.

15.36

A car engine delivers 2.8 * 104 W to its wheels when moving at a constant speed of 18.4 m/s. What is the magnitude of the resistive force (in N) acting on the automobile at that speed? Enter an integer.

1522

A car with a mass of 357 kg is moving to the right with a constant acceleration of 4.3 m/s. What is the total force (in N) on the car? Enter a integer. Round up or down correctly.

1535

By what factor does the drag force on a car increase as its speed increases from 25 km/h to 100 km/h?

16

How much work (in J) must a person do to lift 4 bundles of shingles each weighing 18 pounds 18 feet onto a roof? 1 pound = 4.448 N, 1 foot = 0.305 m Enter an integer. Round up or down correctly.

1758

A stone is thrown directly upward with an initial speed of 5.2 m/s from a height of 18 m. What is the speed of the stone in m/s when it hits the ground? Use g = 9.8 m/s2. Enter a number with 2 digits behind the decimal point.

19.49

An apple at rest weighs 1 N. Now assume the same apple is in free fall near the surface of Earth. Neglect friction. The net force on the apple while it is in free fall is 0 0.1 N 1 N 9.8 N 10 N

1N

Use g = 10 m/s2. Water descends from the top of a tall hydroelectric dam. Its gravitational potential energy is eventually converted into electric energy. How much gravitational potential energy is released when 1000 kg of water descend 200 m to the generators? 2 MJ 200 KJ 50 J 10 KW 2*106 W

2 MJ

A ball is thrown straight upward. It rises in the air and then falls back to earth. Neglect friction. 1) It loses mechanical energy as it rises and gains it back as it falls. 2) On the way up, kinetic energy is converted to potential energy. 3) Its total energy is largest at maximum height. 4) It loses energy throughout its motion. 5) None of the above.

2) On the way up, kinetic energy is converted to potential energy.

Assume there is a completely straight highway from city A to city B, which is 200 km long. You drive along the highway from A to B and back to A in 4 hours. What are the average speed and average velocity of that trip? 1) The average speed and the average velocity are both zero. 2) The average speed is 100 km/hr and the average velocity is zero. 3) The average speed and average velocity are both 100 km/hr. 4) The average speed is zero and the average velocity is 100 km/hr.

2) The average speed is 100 km/hr and the average velocity is zero.

Which of the following observations about the frictional force is incorrect? 1) The magnitude of the force of kinetic friction is always proportional to the normal force. 2) The magnitude of the force of static friction is always proportional to the normal force. 3) The magnitude of the force of static friction is always proportional to the external applied force. 4) The direction of the force of kinetic friction is always opposite to the direction of the relative motion of the object with respect to the contact surface. 5) The direction of the force of static friction is always opposite to the direction of the impending motion of the object with respect to the contact surface. 6) All of the above statements are correct!

2) The magnitude of the force of static friction is always proportional to the normal force.

A box is at rest on a flat table. Which of the following is true? 1) Gravity exerts a force on the box that depends on how big the normal or support force is. 2) The normal force and the gravitational force are equal in magnitude and opposite in direction. 3) The normal force and the gravitational force are an action-reaction pair. 4) The magnitude of normal force depends on the coefficient of static friction between the book and the table.

2) The normal force and the gravitational force are equal in magnitude and opposite in direction

Two objects are traveling around different circular orbits with constant speed. They both have the same centripetal acceleration, but object A is traveling twice as fast as object B. The orbit radius for object A is 1) the same as the orbit for object B. 2) four times the orbit for object B. 3) one-half the orbit for object B. 4) one-fourth the orbit for object B. 5) twice the orbit for object B.

2) four times the orbit for object B.

A force of 20 N in the positive x-direction accelerates an object with acceleration a = 2 m/s2. When the object is moving with velocity v = 10 m/s, an additional force of 10 N in the negative x-direction is applied. Which statement is true? 1. The object now accelerates with acceleration a = -1 m/s2 in the negative x-direction. 2. The object now accelerates with acceleration a = 1 m/s2 in the positive x-direction. 3. The object now moves with constant velocity. 4. The objects slows down and comes to a stop.

2. The object now accelerates with acceleration a = 1 m/s2 in the positive x-direction.

A stone is thrown directly upward with an initial speed of 9.3 m/s from a height of 4.8 m. After what time interval (in s) does the stone strike the ground? Use g = 9.8 m/s2. Enter a number with 2 digits behind the decimal point.

2.32

A 5 kg object is sliding on a surface with a coefficient of kinetic friction of 0.79. If at t = 0 it has a speed of 22 m/s, at what time (in s) will it come to rest? Let g = 9.8 m/s2. Enter a number with one digit after the decimal point.

2.8

The mass of atoms is often given in atomic mass units (u). (1 u = 1.66*10-27 kg) The mass of a hydrogen atom is 1 u, the mass of a carbon atom is 12 u, and the mass of a oxygen atom is 16 u. Calculate the mass, in kg, of a water molecule, H2O 17 18 2.99*10^-26 7.3*10^-26 44*10^-27

2.99 x 10^-26

A crane lifts a 100 kg object to a height of 10 m in 5 s. What is its power output? 1. 200W 2. 2000 W 3. 4000 W 4. 20000 W 5. 100000 W

2000 W

The mass of a a satellite in geostationary orbit is 968 kg. The mass of Earth is 5.97*1024 kg. Because of the force Earth exerts on the satellite, it accelerates. The magnitude of the acceleration is 0.223 m/s2, and it is directed towards Earth. What is the magnitude of the force in N the satellite exerts on Earth? Enter an integer, Round up or down correctly.

216

An 8.5 kg object gains height 8.8 while being accelerated from rest to a final speed of 7.3 m/s by an external force. What was the net work (in J) done on the object? Let g = 9.8 m/s2. Enter an integer.

226

An 3.2 kg object gains height 5.7 while being accelerated from rest to a final speed of 6.3 m/s by an external force. What was the work (in J) done on the object by this force? Let g = 9.8 m/s2. Enter an integer.

242

Suppose you do 1000 J of work on a 4 kg object, and all the work goes into lifting it above the ground. How high above the ground will the object be when all the work has been done? 250 m 100 m 25 m 500 m 1000 m

25m

When struck by a club, a golf ball initially at rest acquires a speed of 31 m/s. If the ball is in contact with the club for 1.17 ms, what is the magnitude of the average acceleration (in m/s2)?

26500

Find the magnitude of the average force (in N) needed to bring a 1714 kg car to rest from a speed of 74 km/h in a distance of 131 m. Enter an integer. Round up or down correctly.

2764

You walk in a given direction for 10 m during the first 3 seconds of a trip and then 20 m during the next 7 seconds. Your average speed is equal to 2.9 m/s. 15 m/s. 3 m/s. 4 m/s. 6.2 m/s.

3 m/s

You are cutting wood with a hand saw. You have to push the saw away from you as it moves away from you and pull it towards you as it moves towards you. When are you doing positive work on the saw? 1) You are not doing work on the saw, the saw is doing work for you. 2) Only when pushing it away from you. 3) When pushing it away from you and when pulling it towards you. 4) Only when pulling it towards you.

3) When pushing it away from you and when pulling it towards you.

Can an objects velocity change direction when its acceleration is constant? 1) No, this is not possible because it is always speeding up. 2) No, this is not possible because it is always speeding up or always slowing down, but it can never turn around. 3) Yes, this is possible, and a rock thrown straight up is an example. 4) Yes, this is possible, and a car that starts from rest, speeds up, slows to a stop, and then backs up is an example. 5) Yes, this is possible, but then the net force must change direction.

3) Yes, this is possible, and a rock thrown straight up is an example.

You paddle in a Kayak across a calm mountain lake. Each time you pull the paddle backward through the water, from the front of the boat to its rear, the water exerts a force on the paddle that is 1) in the backwards direction, towards the rear of the boat. 2) sideways, towards the boat. 3) in the forward direction, towards the front of the boat. 4) sideways, away from the boat.

3) in the forward direction, towards the front of the boat.

A bungee jumper jumps from a bridge. Describe what happens to the jumper's kinetic and (gravitational and elastic) potential energy right after the jumper has reached the bottom of his descent and is pulled back up? 1) kinetic energy decreases, potential energy increases 2) kinetic energy stays the same, potential energy increases 3) kinetic energy increases, potential energy decreases 4) kinetic energy increases, potential energy stays the same 5) kinetic energy increases, potential energy increases

3) kinetic energy increases, potential energy decreases

An object is thrown straight up. At the top of its path 1) the velocity is zero and the acceleration is zero. 2) the velocity is zero and the acceleration is equal to the weight. 3) the velocity is zero and the acceleration is equal to g pointing down. 4) the velocity is down and the acceleration is equal to g pointing down. 5) the velocity is up and the acceleration is zero.

3) the velocity is zero and the acceleration is equal to g pointing down

A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed v0. If the woman doubles the constant horizontal force that she exerts on the box, and the force resisting the motion of the box does not change, the box then moves 1) with constant speed, that is double the speed v0. 2) for a while with a speed that is constant and greater than the speed v0, then with a speed that increases thereafter. 3) with constantly increasing speed. 4) with a constant speed that is greater than the speed v0, but not necessarily twice as great. 5) for a while with increasing speed, then with decreasing speed.

3) with constantly increasing speed.

A girl pulling a sled exerts a 20 N force horizontally for 40 s. How much power does she generate while moving the sled 60 m? 60 W 20 W 40 W 30 W 120 W

30 W

A 83 kg runner with a speed of 6.4 m/s makes a sharp turn with a radius of 1.1 m to avoid a collision. What is the magnitude of the frictional force (in N) the ground exerts on the runner during the turn? Enter an integer. Round up or down correctly.

3091

An ideal spring with a spring constant of 1.6 N/cm and an equilibrium length of 28 cm hangs vertically from the ceiling. A 1.1 kg mass is attached to it. After all motion has damped out, what is the new length of the spring in cm? Enter a number with 1 digit behind the decimal point Let g = 9.8 m/s2..

34.7

You have watched one too many old cartoons and decide to drive around town with a giant spring that is 4 m long and attached to the front of your car. You decide to help a semi truck that is stuck and try to push them with your car. You take a running start, and when you contact the truck the spring in your car compresses 3 m. During which portion of the compression did you do the most work on the spring? 1) No work was done on the spring. 2) During the first meter 3) The work done is equal for all segments. 4) During the third meter. 5) During the second meter.

4) During the third meter

Your hands push on a heavy box to slide it across the floor with constant velocity. The other force of the action/reaction pair is 1) friction pushing backward on the floor. 2) gravity pulling downward on the box. 3) friction pushing backward on the box to make the net force on the box zero. 4) the box pushing backward against your hands. 5) the normal force pushing up on the box

4) the box pushing backward against your hands.

You put your book on the bus seat next to you while the bus is parked at the bus stop. When the bus begins to quickly move away from the bus stop, the book slides towards the back of the seat, without anything pushing it. Why? 1. The back of the seat and the book attract each other. 2. The gravitational force pulls the book backward 3. The motor produces a strong magnetic field. 4. The accelerating bus is not an inertial reference frame.

4. The accelerating bus is not an inertial reference frame.

The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving towards the right. The accelerations of the blocks are related as follows: 1. The acceleration of a is greater than the acceleration of b. 2. The acceleration of a equals the acceleration of b. Both accelerations are greater than zero. 3. The acceleration of b is greater than the acceleration of a. 4. The acceleration of a equals the acceleration of b. Both accelerations are zero. 5. Not enough information is given to answer the question.

4. The acceleration of a equals the acceleration of b. Both accelerations are zero.

A person walks first at a constant speed of 6 m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 4 m/s. What is her average speed over the entire trip? Hint: Assume the distance between A and B is d. How much distance does the person cover on her trip? How long does it take her to cover this distance? 0 5 m/s 3.75 m/s 4,25 m/s 4.8 m/s

4.8 m/s

You operate a 120 W light bulb for 1 hour. How much energy did you use? (1 W = 1 J/s) 432000 J 3.6 MJ 3600 kWh 120 J 3600 J

432000 J

Which is TRUE about vectors and scalars? 1) A vector is a large quantity and a scalar is a small quantity. 2) A scalar quantity has a magnitude and a vector quantity does not. 3) The quantity 20 m/s, north is a speed and as such is a scalar quantity. 4) The quantity 9.8 m/s/s is an acceleration value and as such is a vector quantity. 5) A vector quantity has a direction and a scalar does not.

5) A vector quality has a direction and a scalar does not

A stone is dropped from the roof of a single story building to the surface of the earth. 1) It falls because of a natural tendency of objects to rest on the surface of the earth. 2) It speeds up because the gravitational force gets stronger closer to the earth. 3) It reaches its maximum speed very soon after it is released. 4) It falls because of the combined effect of gravity pushing it downward and the air pushing it downward. 5) It speeds up because of an almost constant force of gravity acting upon it.

5) It speeds up because of an almost constant force of gravity acting upon it.

A woman pulls a crate up a rough, inclined plane at constant speed. Which one of the following statements concerning this situation is false? 1) The gravitational potential energy of the crate is increasing. 2) The net work done by all the forces is zero. 3) The work done on the crate by the normal force is zero. 4) The woman does "positive" work in pulling the crate. 5) The work done on the object by gravity is zero.

5) The work done on the object by gravity is zero.

An elevator is being lifted up an elevator shaft at a constant speed by a steel cable as shown in the figure above. All frictional effects are negligible. In this situation, forces on the elevator are such that 1) none of the above. The elevator goes up because the cable is being shortened, not because an upward force is exerted on the elevator by the cable. 2) the upward force by the cable is greater than the downward force of gravity. 3) the upward force by the cable is greater than the sum of the downward force of gravity and a downward force due to the air. 4) the upward force by the cable is smaller than the downward force of gravity. 5) the upward force by the cable is equal to the downward force of gravity.

5) the upward force by the cable is equal to the downward force of gravity.

Two objects each accelerate at 2.0 m/s2. The first object's mass is 10.0 kg and the second object's mass is 5.0 kg. What is the magnitude of the force on each object? 1. 20N,20N 2. 10 N, 10 N 3. 10 N, 5 N 4. 2 N, 2 N 5. 20N,10N

5. 20N,10N

A spring is stretched by 6.1 cm when a force of 2 N is applied. If a force of 3.9 N is applied, how many additional cm does the spring stretch? Enter a number with two digits behind the decimal point.

5.8

Use g = 10 m/s2. A crane lifts a 200 kg object to a height of 20 m in 8 s. What is its power output? 250 W 4000 J 50 W 40000 J 5000 W

5000 W

A ball is projected horizontally with speed 23.8 m/s from the top of a 26.6 m high building. Neglecting drag, what is its horizontal distance (in m) from the bottom of the building when it hits the ground? Let g = 9.8 m/s2. Enter a number with 1 digit behind the decimal point.

55.5

A 750 kg automobile is traveling horizontally with a speed of 40.0 m/s. What is the automobile's new speed after an additional 600000 J of net work has been done on the car? 1. 28.3 m/s 2. 56.6 m/s 3. 80 m/s 4. 160 m/s 5. Its speed does not change.

56.6 m/s

Car 1 starts from rest along a straight highway with constant acceleration a = 1 m/s2. Car 2 passes car 1 with constant velocity of 120 km/hr. Which car is acted on by a larger net force? Car 1 Car 2 Both cars are acted on by the same non-zero net force. The net force on both cars is zero.

car 1

A block slides on a track from A to B to C to D. The section from A to B to C is frictionless, but for the section from C to D the coefficient of friction is not zero. Is the block's mechanical (ordered) energy increasing, decreasing, or constant in (a) region AB, (b) region BC, and (c) region CD?

constant, constant, decreasing

In order to do a positive amount of work you must exert a force and move in the direction of the force. exert a force and just move. exert a force or move. change an object's position. exert a force and not move.

exert a force and move in the direction of the force.

A small metal cylinder rests on a circular turntable, rotating at a constant speed, as illustrated in the diagram above. Which of the sets of vectors best describes the velocity, acceleration, and net force acting on the cylinder at the position indicated in the diagram?

force and acceleration pointing down, velocity pointing right (D)

In the absence of air resistance, a ball of mass m is tossed upward to reach a height of 20 m. At the 15 m position, 3/4 of the way up, the net force on the ball is (1/4)mg zero, since there is no resistance. mg undefined (3/4)mg

mg

(A) Can two force vectors of unequal magnitude sum to zero net force? (B) Can three force vectors of equal magnitude sum to zero net force?

no, yes

Is it possible to have motion in the absence of a force? No. Only in a non-inertial frame. Only in outer space. Only in a moving frame. None of the above.

none of the above

Which of the following statements about distance and/or displacement are TRUE? (1) Distance is a vector quantity and displacement is a scalar quantity. (2) If a person walks in a straight line and never changes direction, then the distance and the magnitude of the displacement are exactly the same. (3) The diagram below depicts the path of a person walking from position A to B back to C to and then to D. The distance traveled is 90 yds. (4) For the same diagram below, the displacement of the person walking from A to B to C to D is 50 yds.

only statements 2 and 3

The positions of two blocks at successive 0.20-second time intervals are represented by the numbered squares in the figure below. The blocks are moving towards the right. Are the blocks accelerating? Yes, both blocks are accelerating No Only the upper block Only the lower block

only the upper block

In how many of the following situations does the car have a westward acceleration? -- The car travels westward at constant speed. -- The car travels eastward and speeds up. -- The car travels westward and slows down. -- The car travels eastward and slows down. -- The car starts from rest and moves toward the east.

the car travels westward at constant speed

Newton's 3rd law is also called the law of action and reaction. The "reaction" force does not cancel the "action" force because the action force is greater than the reaction force. they are in the same direction. the reaction force exists only after the action force is removed. the reaction force is greater than the action force. they act on different bodies.

they act on different bodies

Refer to the diagram below. Blocks I and II, each with a mass of 1 kg, are hung from the ceiling of an elevator by ropes 1 and 2. What is the force exerted by rope 1 on block I when the elevator is travelling upward at a constant speed of 2.0 m/s? ~2 N ~10 N ~12 N ~20 N ~22 N

~10N

A mass m is lowered gently onto a vertical spring of length L with spring constant k until it just touches the spring. Let y be the distance the spring is compressed and v be the velocity of the mass. The mass is released from rest. Which of the following is the equation for conservation of energy? ½mv2 + ½ky2 + mgy = mgL ½mv2 + ½ky2 + mg(L - y) = mgL ½mv2 + ½k(L - y) 2 + mg(L - y) = mgL ½mv2 + ½k(L - y) 2 + mgy = mgL ½mv2 + ½ky2 + mgy = 0

½mv2 + ½ky2 + mg(L - y) = mgL

Consider the following five graphs (note the axes carefully). Which of these represent(s) one-dimensional motion at constant acceleration, including a = 0? All of them I, II and III only. I and II only. V only. I, II, IV and V only.

I, II, IV and V only

A cat runs across the floor from I to II to II without increasing or decreasing his speed. He only changes his direction of motion at II. Can we say for sure that a force was exerted on the cat at II? A. Yes, there had to be a force on the cat at II B. Not necessarily, since no change in the speed of the cat occurred

A. Yes, there had to be a force on the cat at II

Three trajectories labeled A, B, and C are shown below. For which trajectory is the vertical velocity component at launch the greatest? B A C More information is needed to answer the question. All three trajectories have the same initial vertical velocity component at launch.

All three trajectories have the same initial vertical velocity component at launch.

At the same time that a high-speed bullet is fired horizontally from a rifle, another bullet is simply dropped from the same height. Which bullet strikes the ground first? A. The dropped bullet B. The fired bullet C. Both strike at the same time

C. Both strike at the same time

The diagram below depicts two pucks on a frictionless table. Puck II is four times as massive as puck I. Starting from rest, the pucks are pushed across the table from the start to the finish line by two equal forces. Which puck will have the greater kinetic energy upon reaching the finish line? A. I B. II C. They both have the same kinetic energy. D. There is too little information to answer the question.

C. They both have the same kinetic energy

A person walks from A to B along a circular path of radius 10.0 m around 1/2 of the circle. What is the magnitude (in m) of the displacement vector? A. 0 m B. 62.8 m C. 10m D. 5 m E. 31.4 m F. 20m

F. 20m