PHY 121 Exams 1-4
3.33 A child in a boat throws a 6.40-kg package out horizontally with a speed of 10.0 m/s, Fig. 2. Calculate the velocity, in m/s, of the boat immediately after, assuming it was initially at rest. The mass of the child is 26.0 kg, and that of the boat is 45.0 kg. Ignore water resistance. Question options: -2.0 -0.9 0.9 1.2
-0.9
2.8 A wooden block slides directly down an inclined plane, at a constant velocity of 6.0 m/s. What is the coefficient of kinetic friction, if the plane makes an angle of 25° with the horizontal? Question options: 0.37 0.47 0.91 0.42
.47
2.29 During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the ice before it stops. What is the coefficient of kinetic friction between the puck and the ice? Question options: 0.10 0.11 0.12 0.090
0.10
2.25 An object slides on a level surface in the +x direction. It slows and comes to a stop with a constant acceleration of -2.45 m/s2. What is the coefficient of kinetic friction between the object and the floor? Question options: Impossible to determine without knowing the mass of the object. 0.25 4.9 0.50
0.25
3.12 A railroad freight car, mass 15,000 kg, is allowed to coast along a level track at a speed of 4.0 m/s. It collides and couples with a 50,000-kg second car, initially at rest and with brakes released. What is the speed of the two cars after coupling? Question options: 1.2 m/s 0.92 m/s 1.8 m/s 0.46 m/s
0.92 m/s
3.32 Three children are trying to balance on a seesaw, which consists of a fulcrum rock, acting as a pivot at the center, and a very light board 4.2 m long (Fig. 1) Two playmates are already on either end. Boy A has a mass of 60 kg and sits on the left, and girl B a mass of 38 kg and sits on the right. A.Where should girl C, whose mass is 30 kg, place herself so as to balance the seesaw? B. Which side, left or right, should girl C sit? Question options: 2.5 and right 2.5 and left 1.5 and left 1.5 and right
1.5 and right
3.22 A pulsar (a rotating neutron star) emits pulses at a frequency of 0.60 kHz. The period of its rotation is Question options: 17 ms. 1.7 s. 0.017 s. 1.7 ms.
1.7ms
1.22 A boat, whose speed in still water is 8.0 m/s, is directed across a river with a current of 6.0 m/s. What is the speed of the boat as it crosses the river? Question options: 6.0 m/s 10.0 m/s 5.3 m/s 8.0 m/s
10.0
1.13 A cart starts from rest and accelerates at 4 m/s2 for 5.0 s, then maintains that velocity for 10 s, and then slows down at the rate of 2.0 m/s2 for 4.0 s. What is the final speed of the car? Question options: 10 m/s 20 m/s 16 m/s 12 m/s
12m/s
3.31 Amy (150) and Gwen (50lbs) are standing on slippery ice and push off each other. If Amy slides at 6 m/s what speed does Gwen have
18 m/s
3.9 A wheel starts at rest, and has an angular acceleration of 4 rad/s2. Through what angle does it turn in 3.0 s? 18 rad 36 rad 12 rad 9.0 rad
18 rad
1.28 Two forces are acting on an object as shown in the above figure. What is the magnitude of the resultant force? Question options: 200 N 198 N 47.5 N
185N
4.9 A 20.0-kg object is moved from a height of 5.00 m above a floor to a height of 15.0 m above the floor. What is the change in gravitational potential energy? Question options: 1960 J 1030 J 1176 J zero
1960 J
4.7 Car J moves twice as fast as car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car K is Question options: 4 to 1. 2 to 1. 1 to 2. the same.
2 to 1
4.1 A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the 5500 N force? Question options: 3.00 × 104 J -5.20 × 105 J 2.75 × 105 J -2.45 × 105 J
2.75 x 10^5 J
2.4 A sports car of mass 1000 kg can accelerate from rest to 35 m/s in 1.3 s. What is the average forward force on the car? Question options: 1.9 × 10^5 N 2.6 × 10^2 N 2.7 × 10^4 N 3.9 × 10^3 N
2.7x10^4
1.27 A person stands 35.0 m from a flag pole. With a protractor at eye level, he finds that the angle at the top of the flag pole makes with the horizontal is 25.0 degrees. How high is the flag pole? (The distance from his feet to his eyes is 1.7 m.) Question options: 80 m 30 m 20 m 10 m
20m
1.15 In the figure above, what is the velocity at t= 2.5 s? Question options: 10 m/s 20 m/s -4 m/s 0
20m/s
3.25 A 0.300-kg mass, attached to the end of a 0.750-m string, is whirled around in a smooth level table. If the maximum tension that the string can withstand is 250 N, then what maximum linear speed can the mass have if the string is not to break? Question options: 25.0 m/s 22.4 m/s 19.4 m/s 32.7 m/s
25.0 m/s
1.30 A car travels 20 km West, then 20 km South. What is the magnitude of its displacement? Question options: 40 km 0 km 20 km 28 km
28km
3.18 Two children sit on opposite ends of a uniform seesaw which pivots in the center. Child A has mass 50 kg and sits 2.5 m from the center. Child B has mass 40 kg. How far from the center must child B sit for the seesaw to balance? Question options: 3.1 m 2.1 m 1.1 m cannot be determined without knowing the seesaw's mass
3.1 m
3.13 A ball of mass 0.20 kg is dropped from a height of 20 m. Its momentum when it strikes the ground is Question options: 1.5 kg∙m/s. 4.8 kg∙m/s. 2.9 kg∙m/s. 3.9 kg∙m/s.
3.9 kgm/s
4.8 A 20-kg mass, hung onto a spring, causes the spring to stretch 5.0 cm. What is the spring constant? Question options: 50 N/m 100 N/m 3.9 × 103 N/m 4.9 × 103 N/m
3.9 x 10^3
3.2 The bolts on a car wheel require tightening to a torque of 90 N∙m. If a 30 cm long wrench is used, what is the magnitude of the force required when the force applied at 53° to the wrench? 38 N 19 N 380 N 190 N
380 N
3.23 When a light beach ball rolling with a speed of 6.0 m/s collides with a heavy exercise ball at rest, the beach ball's speed after the collision will be, approximately, Question options: 12.0 m/s. 4.0 m/s. 6.0 m/s. 0
4.0 m/s
1.23 An airplane increases its speed from 100 m/s to 160 m/s, at the average rate of 15 m/s2. How much time does it take for the complete increase in speed? Question options: 17 s 0.25 s 4.0 s 0.058 s
4.0s
2.33 An antitank weapon fires a 3.00-kg rocket which acquires a speed of 50.0 m/s after traveling 90.0 cm down a launching tube. Assuming the rocket was accelerated uniformly, what is the average force acted on it? Question options: 2.82 × 103 N 3.62 × 103 N 4.17 × 103 N 2.00 × 103 N
4.17x10^3
4.6 An object slides down a frictionless inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertical height of the plane? Question options: 4.90 m 19.6 m 2.45 m 9.80 m
4.90 m
1.11 A car travels at 15 m/s for 10 s. It then speeds up with a constant acceleration of 2.0 m/s2 for 15 s. At the end of this time, what is its velocity? Question options: 15 m/s 30 m/s 45 m/s 35 m/s
45m/s
1.19 At what angle should a water-gun be aimed in order for the water to land with the greatest horizontal range? Question options: 0° 45° 30° 60°
45°
1.18 A butterfly moves with a speed of 12.0 m/s. The x component of its velocity is 8.00 m/s. The angle between the direction of its motion and the x axis must be Question options: 53.0°. 41.8°. 48.2°. 30.0°.
48.2°
1.24 An object is thrown upward with a speed of 12 m/s on the surface of planet X where the acceleration due to gravity is 1.5 m/s2. What is the maximum height reached by the object? Question options: 144 m 8.0 m 18 m 48 m
48m
3.30 A box slides with initial velocity 10 m/s on a frictionless surface and collides inelastically with an identical box. The boxes stick together after the collision. What is the final velocity?
5 m/s
2.10 Sue and Sean are having a tug-of-war by pulling on opposite ends of a 5.0-kg rope. Sue pulls with a 15-N force. What is Sean's force if the rope accelerates toward Sue at 2.0 m/s2? Question options: 3.0 N 5.0 N 25 N 50 N
5.0
3.15 The bolts on a car wheel require tightening to a torque of 100 N∙m. If a 20 cm long wrench is used, what is the magnitude of the force required when the force is perpendicular to the wrench? Question options: 25 N 50 N 250 N 500 N
500 N
1.1 Starting from city A, a car drives 250 miles east to city B, then 300 miles north to city C, and finally 700 miles west to city D. What is the distance between city A and city D? Question options: 600 mi 400 mi 500 mi 300 mi
500mi
2.11 The coefficient of static and kinetic frictions between a 3.0-kg box and a desk are 0.40 and 0.30, respectively. What is the net force on the box when a 15 N horizontal force is applied to the box? Question options: 6.2 N 8.8 N zero 12 N
6.2 N
1.26 How many meters is sixty kilometers? Question options: 60,000 m 600,000 m 60 m 0.06 m
60,000m
1.12 An object moves 5.0 m north and then 3.0 m south. Find both the distance traveled and the magnitude of the displacement vector. Question options: 2.0 m, 8.0 m 8.0 m, 2.0 m 2.0 m, 2.0 m 8.0 m, 8.0 m
8.0 m, 2.0 m
1.14 If you are driving 72 km/h along a straight road and you look to the side for 4.0 s, how far do you travel during this inattentive period? Question options: 18 m 40 m 20 m 80 m
80m
1.25 A soccer ball is kicked with a velocity of 25 m/s at an angle of 45° above the horizontal. What is the vertical component of its acceleration as it travels along its trajectory? Question options: 9.80 m/s2 downward (9.80 m/s2) × sin (45°) upward (9.80 m/s2) upward (9.80 m/s2) × sin (45°) downward
9.8 m/s^2 downward
1.10 A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff. A stop watch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.3 s. What is the height of the cliff? Question options: 77 m 91 m 43 m 22 m
91m
1.7 The slope of a velocity versus time graph gives Question options: displacement acceleration position velocity
Acceleration
1.4 If the position versus time graph of an object is a horizontal line, the object is Question options: moving with constant non-zero acceleration at rest moving with infinite speed. moving with constant non-zero speed
At rest
1.2 A new car manufacturer advertises that their car can go "from zero to sixty in 8 s". This is a description of Question options: average acceleration average speed instantaneous acceleration instantaneous speed
Average Acceleration
2.17 Two toy cars (16 kg and 2.0 kg) are released simultaneously on an inclined plane that makes an angle of 30° with the horizontal. Make a statement which best describes their acceleration after being released. Question options: The 2.0-kg car accelerates 8 times faster than the 16-kg car. The 16-kg car accelerates 8 times faster than the 2.0-kg car. none of the above Both cars accelerate at the same rate.
Both cars accelerate at the same rate
3.11 A small object collides with a large object and sticks. Which object experiences the larger magnitude of momentum change? Question options: cannot be determined from the information given the small object Both objects experience the same magnitude of momentum change. the large object
Both objects experience the same magnitude of momentum change
1.20 Suppose a ball is thrown straight up. What is its acceleration just before it reaches its highest point? Question options: slightly greater than g exactly g slightly less than g zero
Exactly G
3.19 An ice skater puls in his outstretched arms close to his body while in a spin. What happens to his rotational speed about the axis of rotation? Question options: It increases. It decreases. It changes, but it is impossible to tell which way. It does not change.
It increases
3.6 A child falls sideways off a sled while sledding on frictionless ice. What happens to the velocity of the sled? It decreases. cannot be determined from the information given It remains the same. It increases.
It remains the same
1.8 Suppose a ball is thrown straight up. Make a statement about the velocity and the acceleration when the ball reaches the highest point. Question options: Both its velocity and its acceleration are zero Its velocity is not zero and its acceleration is zero Neither its velocity nor its acceleration is zero Its velocity is zero and its acceleration is not zero
Its velocity is zero and its acceleration is not zero
2.23 A horizontal force accelerates a box from rest across a horizontal surface (friction is present) at a constant rate. The experiment is repeated, and all conditions remain the same with the exception that the horizontal force is doubled. What happens to the box's acceleration? Question options: It increases to more than double its original value. It increases somewhat. It increases to less than double its original value. It increases to exactly double its original value.
Less than double
2.24 A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The normal reaction force exerted by the plane on the block is Question options: Mg sin θ. Mg cos θ. zero, since the plane is frictionless. Mg.
Mgcosθ
3. 1 What are the units of a spring constant, k? it is a unitless value N*m N/m N
N/m
1.29 A stone is thrown horizontally from the top of a tower at the same instant a ball is dropped vertically. Which object is traveling faster when it hits the level ground below? Question options: the ball it is impossible to tell from the information given Neither, since both are traveling at the same speed. the stone
Neither, since both are traveling at the same speed.
2.20 Two cars collide head-on. At every moment during the collision, the magnitude of the force the first car exerts on the second is exactly equal to the magnitude of the force the second car exerts on the first. This is an example of Question options: Newton's second law. Newton's third law Newton's first law Newton's law of gravitation.
Newton's third law
3.17 A heavy boy and a light girl are balanced on a massless seesaw. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw? Question options: The side the boy is sitting on will tilt downward. The side the girl is sitting on will tilt downward. It is impossible to say without knowing the masses and the distances. Nothing, the seesaw will still be balanced.
Nothing, the seesaw will still be balanced.
3.21 Angular displacement is usually express in units of Question options: radians. meters arcs. revolutions.
Radians
4.3 If you push twice as hard against a stationary brick wall, the amount of work you do Question options: doubles. remains constant but non-zero. remains constant at zero. is cut in half.
Remains constant at zero
1.21 Suppose a ball is thrown straight up. What is its acceleration just before it reaches its highest point? Question options: The acceleration must be constantly increasing. The acceleration must be equal to zero. The acceleration must be a constant non-zero value. The acceleration must be constantly decreasing.
The acceleration must be a constant non-zero value.
2.3 A 15-ton truck collides with a 1500-lb car and causes a lot of damage to the car. Since a lot of damage is done on the car Question options: the truck did not slow down during the collision. the force on the truck is greater than the force on the car. the force on the truck is equal to the force on the car. the force on the truck is smaller tan the force on the car.
The force on the truck is equal to the force on the car
3.10 A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the average collision force is correct? It is impossible to tell since the masses and velocities are not given. The small car experiences the greater average force. The small car and the truck experience the same average force. The truck experiences the greater average force.
The small car and the truck experience the same average force.
3.14 A 4.0-kg object moves to the right at 5.0 m/s. It collides head-on with a 10.0-kg object moving to the left at 2.0 m/s. Which statement is correct? Question options: The total momentum both before and after the collision is 40 kg∙m/s. The total momentum both before and after the collision is zero. None of the above is true. The total momentum before the collision is 40 kg∙m/s, and after the collision is 0 kg∙m/s.
The total momentum both before and after the collision is zero.
3.3 An object moves in a circular path at a constant speed. Compare the direction of the object's velocity and acceleration vectors. The question is meaningless, since the acceleration is zero The vectors point in opposite directions. The vectors are perpendicular. Both vectors point in the same direction.
The vectors are perpendicular.
2.9 You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes to an immediate stop. What force caused you to fall forward? Question options: There is not a force leading to your fall gravity force due to friction between you and the floor of the bus normal force due to your contact with the floor of the bus
There is not a force leading to your fall
2.1 When you sit on a chair, the resultant force on you is down up zero depending on your weight
Up
1.3 Which one of the following is an example of a vector quantity? Question options: area velocity mass distance
Velocity
1.6 The slope of a position versus time graph gives Question options: position acceleration displacement velocity
Velocity
2.5 Is it possible for an object moving with a constant speed to accelerate? Explain. Question options: Yes, if an object is moving it can experience acceleration Yes, although the speed is constant, the direction of the velocity can be changing. No, if the speed is constant then the acceleration is equal to zero. No, an object can accelerate only if there is a net force acting on it
Yes, although the speed is constant, the direction of the velocity can be changing
1.9 If you run a complete loop around an outdoor track (400m), in 100 s, your average velocity is Question options: 0.25 m/s zero 40,000 m/s 4.0 m/s
Zero
4.5 If you walk 5.0 m horizontally forward at a constant velocity carrying a 10-N object, the amount of work you do is more than 50 J. equal to 50 J. less than 50 J, but more than 0 J. zero.
Zero
2.18 A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that Question options: a frictional force is acting on it. it may be accelerating. it is not acted on by appreciable gravitational force. a net downward force is acting on it.
a frictional force is acting on it.
2.6 A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that Question options: a net downward force is acting on it. a frictional force is acting on it. it is not acted on by appreciable gravitational force. it may be accelerating
a frictional force is acting on it.
2.21 A net force F accelerates a mass m with an acceleration a. If the same net force is applied to mass 2m, then the acceleration will be Question options: 4a. 2a. a/4. a/2.
a/2
2.30 A net force F acts on a mass m and produces an acceleration a. What acceleration results if a net force 2F acts on mass 4m? Question options: a/2 8a 4a 2a
a/2
3.26 A net force of 200 N acts on a 100-kg boulder, and a force of the same magnitude acts on a 130-g pebble. How does the rate of change of the boulder's momentum compare to the rate of change in the pebble's momentum? equal to greater than less than
equal to
2.22 A stone is thrown straight up. At the top of its path, the net force acting on it is Question options: instantaneously equal to zero greater than zero, but less than its weight. greater than its weight. equal to its weight.
equal to its weight.
2.13 An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving up at constant speed. What is the tension in the string? Question options: greater than mg less than mg exactly mg cannot be determined without knowing the speed.a
exactly mg
3.29 You tee up a golf ball and drive it down the fairway. Assume that the collision of the golf club and ball is elastic. When the ball leaves the tee, how does it speed compare to the speed of the golf club?
greater than
1.17 Ignoring air resistance, the horizontal component of a projectile's acceleration Question options: continuously increases continuously decreases remains a non-zero constant is zero
is zero
4.4 What is the correct unit of work expressed in SI units? Question options: kg2 m/s2 kg m/s2 kg m2/s kg m2/s2
kg m^2/s^2
2.26 A person is standing on a scale in an elevator accelerating downward. Compare the reading on the scale to the person's true weight. Question options: equal to their true weight greater than their true weight less than their true weight zero
less than their true weight
2.31 The acceleration due to gravity is lower on the Moon than on Earth. Which of the following is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth? Question options: Both mass and weight are the same. Mass is same, weight is less. Mass is less, weight is same. Both mass and weight are less
mass is the same, weight is less
3.7 When a cannon fires a cannonball, the cannon will recoil backward because the momentum of the cannonball and cannon is conserved. momentum of the cannon is greater than the energy of the cannonball. energy of the cannonball and cannon is conserved. energy of the cannon is greater than the energy of the cannonball.
momentum of the cannonball and cannon is conserved.
2.12 A pilot executes a vertical dive then follows a semi-circular arc until it is going straight up. Just as the plane is at its lowest point, the force on him is more than mg, and pointing up. more than mg, and pointing down. less than mg, and pointing down. less than mg, and pointing up.
more than mg, and pointing up.
2.2 When the rocket engines on the starship NO-PAIN-NO-GAIN are suddenly turned off, while traveling in empty space, the starship will stop immediately go faster and faster. slowly slow down, and then stop. move with constant speed.
move with constant speed.
2.28 In the absence of an external force, a moving object will Question options: stop immediately. move with constant velocity. slow down and eventually come to a stop. go faster and faster.
move with constant velocity
1.5 If the velocity versus time graph of an object is a straight line making an angle of 30 degrees with the time axis, the object is Question options: moving with constant non-zero speed moving with constant non-zero acceleration moving with infinite speed at rest
moving with constant non-zero acceleration
3.4 A car goes around a curve of radius r at a constant speed v. Then it goes around the same curve at half of the original speed. What is the centripetal force on the car as it goes around the curve for the second time, compared to the first time? one-fourth as big four times as big twice as big half as big
one-fourth as big
3.20 Angular acceleration is expressed in units of Question options: meters per second squared. arcs per second squared. radians per second squared. alphas per second squared.
radians per second squared
1.16 Ignoring air resistance, the horizontal component of a projectile's velocity Question options: continuously decreases remains constant is zero continuously increases
remains constant
3.27 An open cart rolls along a frictionless track while it is raining. As it rolls, what happens to the speed of the cart as the rain collects in it?
slows down
2.32 An object is placed on an inclined plane. The angle of incline is gradually increased until the object begins to slide. The angle at which this occurs is θ. What is the coefficient of static friction between the object and the plane? Question options: tan θ sin θ cos θ 1/tan θ
tanθ
2.16 If you push a 4.0-kg mass with the same force that you push a 10-kg mass from rest, Question options: the 10-kg mass accelerates 2.5 times faster than the 4.0-kg mass. None of the above is true. both masses accelerate at the same rate. the 4.0-kg mass accelerates 2.5 times faster than the 10-kg mass.
the 4.0-kg mass accelerates 2.5 times faster than the 10-kg mass
3.8 A rubber ball and a lump of putty have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The putty sticks to the wall. Which objects experiences the greater momentum change? Both experience the same momentum change. cannot be determined from the information given the putty the ball
the ball
2.15 Which of Newton's laws best explains why motorists should buckle-up? Question options: the first law the third law the law of gravitation the second law
the first law
4.2 The quantity Fd/t is Question options: the power supplied to the object by the force. the kinetic energy of the object the work done on the object by the force. the potential energy of the object
the power supplied to the object by the force
3.5 Two equal forces are applied to a door. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force exerts the greater torque? the second at the doorknob both exert zero torques the first at the midpoint both exert equal non-zero torques
the second at the doorknob
3.28 A person stands under an umbrella during a rainstorm. Later the rain turns to hail, although the number of "drops" hitting the umbrella per time and their speed remains the same. Which case requires more force to hold the umbrella?
when it is hailing
2.7 It's more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because Question options: µs< µk µs > µk initially, the normal force is not perpendicular to the applied force. the normal force is greater when the carton is at rest.
µs > µk
