Deck 5: Applying Newtons Laws

Question 1

General questions: You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes to an immediate stop. The force acting on you that causes you to fall forward is

A) the force of gravity.
B) the normal force due to your contact with the floor of the bus.
C) the force due to static friction between you and the floor of the bus.
D) the force due to kinetic friction between you and the floor of the bus.
E) No forces were acting on you to cause you to fall.

Answer 1

No forces were acting on you to cause you to fall.

Question 2

General questions: You swing a bat and hit a heavy box with a force of 1500 N. The force the box exerts on the bat is

A) exactly 1500 N only if the box does not move.
B) exactly 1500 N whether or not the box moves.
C) greater than 1500 N if the box moves.
D) less than 1500 N if the box moves.
E) greater than 1500 N if the bat bounces back.

Answer 2

exactly 1500 N whether or not the box moves.

Question 3

General questions: A 615 N student standing on a scale in an elevator notices that the scale reads 645 N. From this information, the student knows that the elevator must be moving

A) downward.
B) upward.
C) You cannot tell if it is moving upward or downward.

Answer 3

You cannot tell if it is moving upward or downward.

Question 4

General questions: A car is being towed at constant velocity on a horizontal road using a horizontal chain. The tension in the chain must be equal to the weight of the car in order to maintain constant velocity.

Question 5

General questions: Consider what happens when you jump up in the air. Which of the following is the most accurate statement?

A) It is the upward force exerted by the ground that pushes you up, but this force cannot exceed your weight.
B) You are able to spring up because the earth exerts a force upward on you that is greater than the downward force you exert on the earth.
C) Since the ground is stationary, it cannot exert the upward force necessary to propel you into the air. Instead, it is the internal forces of your muscles acting on your body itself that propels your body into the air.
D) When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air.
E) When you jump up the earth exerts a force F₁ on you and you exert a force F₂ on the earth. You go up because F₁ > F₂.

Question 6

General questions: A stalled car is being pushed up a hill at constant velocity by three people. The net force on the car is

A) zero.
B) up the hill and equal to the weight of the car.
C) down the hill and equal to the weight of the car.
D) up the hill and greater than the weight of the car.
E) down the hill and greater than the weight of the car.

Question 7

General questions: Two objects, each of weight W, hang vertically by spring scales as shown in the figure. The pulleys and the strings attached to the objects have negligible weight, and there is no appreciable friction in the pulleys. The reading in each scale is

A) W.
B) more than W, but not quite twice as much.
C) less than W.
D) 2W.
E) more than 2W.

Question 8

General questions: A dog is standing in the bed of a pickup truck. The bed is coated with ice, causing the force of friction between the dog and the truck to be zero. The truck is initially at rest, and then accelerates to the right, moving along a flat road. As seen from a stationary observer (watching the truck move to the right), the dog

A) does not move left or right, but the back of the truck moves towards the dog.
B) moves to the right, but not as quickly as the truck is moving to the right, causing it to slide towards the back of the truck.
C) moves to the right at the same rate as the truck, so it doesn't slide.
D) moves to the left, as the truck moves to the right, causing the dog to slide towards the back of the truck.

Question 9

General questions: Suppose you are playing hockey on a new-age ice surface for which there is no friction between the ice and the hockey puck. You wind up and hit the puck as hard as you can. After the puck loses contact with your stick, the puck will

A) start to slow down.
B) not slow down or speed up.
C) speed up a little, and then slow down.
D) speed up a little, and then move at a constant speed.

Question 10

General questions: An object is moving to the right, and experiencing a net force that is directed to the right. The magnitude of the force is decreasing with time. The speed of the object is

A) increasing.
B) decreasing.
C) constant in time.

Question 11

General questions: In order to lift a bucket of concrete, you must pull up harder on the bucket than it pulls down on you.

Question 12

General questions: In order to get an object moving, you must push harder on it than it pushes back on you.

Question 13

General questions: A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15° above the horizontal. If T is the tension in this wire, then

A) T = ma.
B) T > ma.
C) T < ma.

Question 14

General questions: Point P in the figure indicates the position of an object traveling at constant speed clockwise around the circle. Which arrow best represent the direction the object would travel if the net external force on it were suddenly reduced to zero?

A)

B)

C)

D)

E)

Question 15

General questions: A 20-tonne truck collides with a 1500-kg car and causes a lot of damage to the car. During the collision

A) the force on the truck due to the collision is slightly greater than the force on the car.
B) the force of on the truck due to the collision is exactly equal to the force on the car.
C) the force on the car due to the collision is much greater than the force on the truck.
D) the car and the truck have the same magnitude acceleration.

Question 16

General questions: A fish weighing 16 N is weighed using two spring scales, each of negligible weight, as shown in the figure. What will be the readings of the scales?

A) The bottom scale will read 16 N, and the top scale will read zero.
B) Each scale will read 16 N.
C) The top scale will read 16 N, and the bottom scale will read zero.
D) The scales will have different readings, but the sum of the two readings will be 16 N.
E) Each scale will read 8 N.

Question 17

General questions: An object is moving forward with a constant velocity. Which statement about this object MUST be true?

A) The net force on the object is zero.
B) The net force on the object is in the forward direction.
C) No forces are acting on the object.
D) The acceleration of the object is in the forward direction.

Question 18

General questions: Which one of the following free-body diagrams best represents the free-body diagram, with correct relative force magnitudes, of a person in an elevator that is traveling upward with an unchanging velocity? _f is the force of the floor on the person and
_g is the force of gravity on the person.

A)

B)

C)

D)

E)

Question 19

General questions: A ball is tossed vertically upward. When it reaches its highest point (before falling back downward)

A) the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward.
B) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is zero.
C) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is directed downward.
D) the velocity and acceleration reverse direction, but the force of gravity on the ball remains downward.
E) the velocity, acceleration, and the force of gravity on the ball all reverse direction.

Question 20

General questions: Which one of the following free-body diagrams best represents the free-body diagram, with correct relative force magnitudes, of a person in an elevator that is traveling upward but is gradually slowing down at a rate of 9 m/s2? _f is the force of the floor on the person and
_g is the force of gravity on the person.

A)

B)

C)

D)

E)

Question 21

Slanted surfaces with friction: A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point down the ramp.

Question 22

Uniform circular motion: A string is attached to the rear-view mirror of a car. A ball is hanging at the other end of the string. The car is driving around in a circle, at a constant speed. Which of the following lists gives all of the forces directly acting on the ball?

A) tension and gravity
B) tension
C) tension, gravity, and the centripetal force
D) tension, gravity, the centripetal force, and friction

Question 23

Newton's second law: The following four forces act on a 4.00 kg object:

₁ = 300 N east


₂ = 700 N north


₃ = 500 N west


₄ = 600 N south
What is the acceleration of the object?

A) 224 N in a direction 63.4° north of west
B) 300 N in a direction 63.4° north of west
C) 300 N in a direction 26.6° north of west
D) 224 N in a direction 26.6° north of west
E) 2100 N in a direction 26.6° north of west

Question 24

Newton's second law: A block lies on a horizontal frictionless surface. A horizontal force of 100 N is applied to the block giving rise to an acceleration of 3.0 m/s².
(a) Determine the mass of the block.
(b) Calculate the distance the block will travel if the force is applied for 10 s.
(c) Calculate the speed of the block after the force has been applied for 10 s

Question 25

Slanted surfaces without friction: Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest.

A) It takes the lighter object 5 times longer to reach the bottom of the incline than the heavier object.
B) It takes the lighter object 10 times longer to reach the bottom of the incline than the heavier object.
C) It takes the heavier object 5 times longer to reach the bottom of the incline than the lighter object.
D) It takes the heavier object 10 times longer to reach the bottom of the incline than the lighter object.
E) The two objects reach the bottom of the incline at the same time.

Question 26

Banked curves: Suppose a highway curve is properly banked to eliminate friction for a speed of 45 km/h. If your tires were bald and you wanted to avoid sliding on the road, you would have to drive

A) somewhat below 45 km/h.
B) somewhat above 45 km/h.
C) at exactly 45 km/h.

Question 27

Multiple-object systems without friction: Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P. The tension in the wire is T (see figure). Which one of the following relationships between T and P must be true?

A) T > P
B) T = P
C) P + T = 125 N
D) P = T + 25 N
E) P = T + 100 N

Question 28

Multiple-object systems without friction: Two unequal masses M and m (M > m) are connected by a light cord passing over a pulley of negligible mass, as shown in the figure. When released, the system accelerates. Friction is negligible. Which figure below gives the correct free-body force diagrams for the two masses in the moving system?

A)

B)

C)

D)

Question 29

Multiple-object systems without friction: Two objects having masses m₁ and m₂ are connected to each other as shown in the figure and are released from rest. There is no friction on the table surface or in the pulley. The masses of the pulley and the string connecting the objects are completely negligible. What must be true about the tension T in the string just after the objects are released?

A) T = m₂g
B) T > m₂g
C) T < m₂g
D) T = m₁g
E) T > m₁g

Question 30

Newton's second law: The figure shows an acceleration-versus-force graph for three objects pulled by rubber bands. The mass of object 2 is 36 kg. What are the masses of objects 1 and 3?

A) 14 kg and 90 kg
B) 72 kg and 18 kg
C) 90 kg and 18 kg
D) 14 kg and 72 kg

Question 31

Air resistance: When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal speed. Once he has reached terminal speed

A) his acceleration is equal to g.
B) the force of air drag on him is equal to zero.
C) the force of air drag on him is equal to g.
D) his speed is equal to g.
E) the force of air drag on him is equal to his weight.

Question 32

Slanted surfaces without friction: A box slides down a frictionless plane inclined at an angle θ above the horizontal. The gravitational force on the box is directed

A) parallel to the plane in the same direction as the movement of the box.
B) parallel to the plane in the opposite direction as the movement of the box.
C) perpendicular to the plane.
D) vertically.
E) at an angle θ below the inclined plane.

Question 33

Newton's second law: A 7.0-kg object is acted on by two forces. One of the forces is 10.0 N acting toward the east. Which of the following forces is the other force if the acceleration of the object is 1.0 m/s² toward the east?

A) 6.0 N east
B) 3.0 N west
C) 12 N east
D) 9.0 N west
E) 7.0 N west

Question 34

General questions: You are seated in a bus and notice that a hand strap that is hanging from the ceiling hangs away from the vertical in the backward direction. From this observation, you can conclude that

A) the velocity of the bus is forward.
B) the velocity of the bus is backward.
C) You cannot conclude anything about the direction of the velocity of the bus.

Question 35

Air resistance: Suppose the force of the air drag on an object is proportional to the speed of the object and in the direction opposite the object's velocity. If you throw an object upward, the magnitude of its acceleration is greatest

A) right after the object is released.
B) at the top of its trajectory.
C) The acceleration of the object is the same throughout the entire trajectory.

Question 36

Uniform circular motion: If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out because an outward force balances the pull of gravity on the water.

Question 37

Multiple-object systems without friction: Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be

A) zero.
B) less than F but not zero.
C) equal to F.
D) greater than F.

Question 38

Newton's second law: If a 5.0 kg box is pulled simultaneously by a 10.0 N force and a 5.0 N force, then its acceleration must be

A) 3.0 m/s².
B) 2.2 m/s².
C) 1.0 m/s².
D) We cannot tell from the information given.

Question 39

Equilibrium: A woman is straining to lift a large crate, without success because it is too heavy. We denote the forces on the crate as follows: P is the upward force the woman exerts on the crate, C is the vertical contact force exerted on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the woman is trying unsuccessfully to lift the crate?

A) P + C = W
B) P + C < W
C) P + C > W
D) P = C

Question 40

Slanted surfaces with friction: A brick is resting on a rough incline as shown in the figure. The friction force acting on the brick, along the incline, is

A) zero.
B) equal to the weight of the brick.
C) greater than the weight of the brick.
D) less than the weight of the brick.

Question 41

Newton's second law: In a ballistics test, a 1.50-g bullet is fired through a 28.0-kg block traveling horizontally toward the bullet. In this test, the bullet takes 11.4 ms to pass through the block as it reverses the block's velocity from 1.75 m/s to the right to 1.20 m/s to the left with constant acceleration. Find the magnitude of the force that the bullet exerts on the block during this ballistics test.

Question 42

Newton's second law: A construction worker pulls a box of tools on a smooth horizontal floor with a force of 100 N in a direction of 37.0° above the horizontal. The mass of the box and the tools is 40.0 kg.
(a) Draw a free-body diagram for the box.
(b) Calculate the acceleration of the box.
(c) How hard does the floor push up on the box?

Question 43

Newton's second law: A 60.0-kg person rides in an elevator while standing on a scale. The scale reads 400 N. The acceleration of the elevator is closest to

A) 3.13 m/s² downward.
B) 6.67 m/s² downward.
C) zero.
D) 9.80 m/s² downward.
E) 6.67 m/s² upward.

Question 44

Newton's second law: A 10,000-kg rocket blasts off from earth with a uniform upward acceleration of 2.00 m/s² and feels no air resistance. The upward thrust force its engines must provide during this acceleration is closest to

A) 20,000 N.
B) 980,000 N.
C) 118,000 N.
D) 78,000 N.

Question 45

Newton's second law: An 1100-kg car traveling at 27.0 m/s starts to slow down and comes to a complete stop in 578 m. What is the magnitude of the average braking force acting on the car?

A) 690 N
B) 550 N
C) 410 N
D) 340 N

Question 46

Newton's second law: A 1000-kg car is driving toward the north along a straight horizontal road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest uniformly in a distance of 200 m. What are the magnitude and direction of the net force applied to the car to bring it to rest?

A) 1.00 N north
B) 10.0 × N south
C) 1.00 × N south
D) 1.00 N south
E) 100 N south

Question 47

Newton's second law: The figure shows a graph of the acceleration of an object as a function of the net force acting on it. The mass of this object, in grams, is closest to

A) 130.
B) 11.
C) 89.
D) 8000.

Question 48

Newton's second law: On a horizontal frictionless floor, a worker of weight 0.900 kN pushes horizontally with a force of 0.200 kN on a box weighing 1.80 kN. As a result of this push, which statement could be true?

A) The box will not move because the push is less than its weight.
B) The worker and box will both have an acceleration of 1.08 m/s², but in opposite directions.
C) The worker and box will both have an acceleration of 2.17 m/s², but in opposite directions.
D) The worker will accelerate at 1.08 m/s² and the box will accelerate at 2.17 m/s², but in opposite directions.
E) The worker will accelerate at 2.17 m/s² and the box will accelerate at 1.08 m/s², but in opposite directions.

Question 49

Newton's second law: On its own, a certain tow-truck has a maximum acceleration of 3.0 m/s². What would be the maximum acceleration when this truck was towing a bus of twice its own mass?

A) 2.5 m/s²
B) 2.0 m/s²
C) 1.5 m/s²
D) 1.0 m/s²

Question 50

Newton's second law: The graph in the figure shows the x component of the acceleration of a 2.4-kg object as a function of time (in ms). (a) At what time(s) does the x component of the net force on the object reach its maximum magnitude, and what is that maximum magnitude?
(b) What is the x component of the net force on the object at time t = 0.0 ms and at t = 4.0 ms?

Question 51

Newton's second law: Bumpers on cars are not of much use in a collision. To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm when the car had an initial speed of 2.0 m/s (about 7.2 km/h). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.)

A) 1.8 × 10⁴ N
B) 1.6 × 10⁴ N
C) 5.4 × 10⁴ N
D) 6.5 × 10⁵ N
E) 3.2 × 10⁴ N

Question 52

Newton's second law: The figure shows a graph of the acceleration of a 125-g object as a function of the net force acting on it. What is the acceleration at points A and B?

Question 53

Newton's second law: A box of mass 50 kg is at rest on a horizontal frictionless surface. A constant horizontal force F then acts on the box and accelerates it to the right. It is observed that it takes the box 6.9 seconds to travel 28 meters. What is the magnitude of the force?

Question 54

Newton's second law: A block is on a frictionless horizontal table, on earth. This block accelerates at 1.9 m/ when a horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/s². What is the weight of the block on the moon?

A) 77 N
B) 67 N
C) 58 N
D) 48 N
E) 39 N

Question 55

Newton's second law: A 60.0-kg person rides in elevator while standing on a scale. The elevator is traveling downward but slowing down at a rate of 2.00 m/s². The reading on the scale is closest to

A) 589 N.
B) 708 N.
C) 469 N.
D) 120 N.
E) 349 N.

Question 56

Newton's second law: Two forces act on a object. One force has magnitude 65 N directed 59° clockwise from the positive x-axis, and the other has a magnitude 35 N at 32° clockwise from the positive y-axis. What is the magnitude of this object's acceleration?

A) 1.1 m/s²
B) 1.3 m/s²
C) 1.5 m/s²
D) 1.7 m/s²

Question 57

Newton's second law: A block is on a frictionless horizontal table, on earth. This block accelerates at 3.6 m/ when a horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/ . A horizontal force of 45 N is applied to the block when it is on the moon. What acceleration does this force impart to the block?

A) 1.8 m/
B) 1.6 m/
C) 2.0 m/
D) 2.2 m/
E) 2.3 m/

Question 58

Newton's second law: The International Space Station has a mass of 1.8 × 10⁵ kg. A 70.0-kg astronaut inside the station pushes off one wall of the station so she accelerates at 1.50 m/s². What is the magnitude of the acceleration of the space station as the astronaut is pushing off the wall? Give your answer relative to an observer who is space walking and therefore does not accelerate with the space station due to the push.

A) 5.8 × 10^-4 m/s²
B) 1.50 m/s²
C) 4.7 × 10^-4 m/s²
D) zero
E) 3.9 × 10^-3 m/s²

Question 59

Newton's second law: A 50.0-N box is sliding on a rough horizontal floor, and the only horizontal force acting on it is friction. You observe that at one instant the box is sliding to the right at 1.75 m/s and that it stops in 2.25 s with uniform acceleration. What magnitude force does friction exert on this box?

A) 3.97 N
B) 8.93 N
C) 38.9 N
D) 50.0 N
E) 490 N

Question 60

Newton's second law: A locomotive is pulling 19 freight cars, each of which is loaded with the same amount of weight. The mass of each freight car (with its load) is 37,000 kg. If the train is accelerating at on a level track, what is the tension in the coupling between the second and third cars? (The car nearest the locomotive is counted as the first car, and friction is negligible.)

Question 61

Slanted surfaces without friction: A child on a sled starts from rest at the top of a 15° slope. If the trip to the bottom takes how long is the slope? Assume that frictional forces may be neglected.

A) 293 m
B) 586 m
C) 1130 m
D) 147 m

Question 62

Slanted surfaces without friction: A system comprising blocks, a light frictionless pulley, a frictionless incline, and connecting ropes is shown in the figure. The 9.0-kg block accelerates downward when the system is released from rest. The tension in the rope connecting the 6.0-kg block and the 4.0-kg block is closest to

A) 30 N.
B) 33 N.
C) 36 N.
D) 39 N.
E) 42 N.

Question 63

Friction: A 4.00-kg block rests between the floor and a 3.00-kg block as shown in the figure. The 3.00-kg block is tied to a wall by a horizontal rope. If the coefficient of static friction is 0.800 between each pair of surfaces in contact, what horizontal force F must be applied to the 4.00-kg block to make it move?

A) 16.2 N
B) 54.9 N
C) 21.1 N
D) 23.5 N
E) 78.4 N

Question 64

Slanted surfaces without friction: A block is given a very brief push up a 20.0° frictionless incline to give it an initial speed of 12.0 m/s.
(a) How far along the surface of the plane does the block slide before coming to rest?
(b) How much time does it take to return to its starting position?

Question 65

Multiple-object systems without friction: A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface as shown in the figure. The 6.00-kg block is being pushed by a horizontal 20.0-N force as shown. What is the magnitude of the force that the 6.00-kg block exerts on the 4.00-kg block?

A) 6.00 N
B) 20.0 N
C) 8.00 N
D) 4.00 N
E) 10.0 N

Question 66

Multiple-object systems without friction: The figure shows a 100-kg block being released from rest from a height of 1.0 m. It then takes it 0.90 s to reach the floor. What is the mass m of the other block? The pulley has no appreciable mass or friction.

A) 60 kg
B) 54 kg
C) 48 kg
D) 42 kg

Question 67

Friction: A driver in a car traveling at slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the horizontal road is 0.80, how long will the skid marks be?

A) 26 m
B) 21 m
C) 33 m
D) 24 m

Question 68

Multiple-object systems without friction: A series of weights connected by very light cords are given an upward acceleration of 4.00 m/s² by a pull P, as shown in the figure. A, B, and C are the tensions in the connecting cords. The pull P is closest to

A) 690 N.
B) 490 N.
C) 290 N.
D) 200 N.
E) 50 N.

Question 69

Multiple-object systems without friction: Two objects are connected by a very light flexible string as shown in the figure, where M = 0.60 kg and m = 0.40 kg. You can ignore friction and the mass of the pulley. (a) Draw free-body diagrams for each object.
(b) Calculate the magnitude of the acceleration of each object.
(c) Calculate the tension in the string.

Question 70

Newton's second law: The graph in the figure shows the net force acting on a 3.0-kg object as a function of time. (a) What is the acceleration of this object at time t = 2.0 s?
(b) Draw, to scale, a graph of the acceleration of this object as a function of time over the range t = 0.00 s to t = 7.0 s.

Question 71

Friction: In a shuffleboard game, the puck slides a total of before coming to rest. If the coefficient of kinetic friction between the puck and the horizontal board is 0.28, what was the initial speed of the puck?

A) 8.1 m/s
B) 29.0 m/s
C) 6.5 m/s
D) 7.3 m/s

Question 72

Multiple-object systems without friction: Three boxes in contact rest side-by-side on a smooth, horizontal floor. Their masses are 5.0-kg, 3.0-kg, and 2.0-kg, with the 3.0-kg box in the center. A force of 50 N pushes on the 5.0-kg box, which pushes against the other two boxes.
(a) Draw the free-body diagrams for each of the boxes.
(b) What magnitude force does the 3.0-kg box exert on the 5.0-kg box?
(c) What magnitude force does the 3.0-kg box exert on the 2.0-kg box?

Question 73

Multiple-object systems without friction: The figure shows two 1.0 kg-blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at 2.3 m/s² by force . What is the tension at the top end of rope 1?

A) 18 N
B) 15 N
C) 2.9 N
D) 3.5 N

Question 74

Multiple-object systems without friction: A 20.0-N box rests on a 50.0-N box on a perfectly smooth horizontal floor. When a horizontal 15.0-N pull to the right is exerted on the lower box (see figure), both boxes move together. Find the magnitude and direction of the net external force on the upper box.

Question 75

Multiple-object systems without friction: A series of weights connected by very light cords are given an upward acceleration of 4.00 m/s² by a pull P, as shown in the figure. A, B, and C are the tensions in the connecting cords. The SMALLEST of the three tensions, A, B, and C, is closest to

A) 80.0 N.
B) 196 N.
C) 276 N.
D) 483 N.
E) 621 N.

Question 76

Multiple-object systems without friction: Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure. The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N. What is the mass M?

A) 8.33 kg
B) 33.9 kg
C) 35.0 kg
D) 52.8 kg
E) 95.0 kg

Question 77

Friction: A 50.0-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.300 and the coefficient of kinetic friction is 0.200. What is the friction force on the box if
(a) a horizontal 140-N push is applied to it?
(b) a horizontal 175-N push is applied to it?

Question 78

Multiple-object systems without friction: Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure. The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N. What is the tension in wire A?

A) 87.5 N
B) 245 N
C) 280 N
D) 333 N
E) 517 N

Question 79

Multiple-object systems without friction: A wooden block A of mass 4.0 kg slides on a frictionless table when pulled using a massless string and pulley array by a hanging box B of mass 5.0 kg, as shown in the figure. What is the acceleration of block A as it slides on the frictionless table?
Hint: Think carefully about the acceleration constraint.

A) 4.1 m/s²
B) 3.5 m/s²
C) 3.1 m/s²
D) 2.7 m/s²

Question 80

Friction: A 150-N box is being pulled horizontally in a wagon accelerating uniformly at 3.00 m/s². The box does not move relative to the wagon, the coefficient of static friction between the box and the wagon's surface is 0.600, and the coefficient of kinetic friction is 0.400. The friction force on this box is closest to

A) 450 N.
B) 90.0 N.
C) 60.0 N.
D) 45.9 N.