Question 1

A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. During the collision

Accepted Answer

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. 
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 2

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

Accepted Answer

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

Question 3

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?

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 4

A system comprised blocks, a light frictionless pulley, and connecting ropes is shown in the figure. The 9.0-kg block is on a perfectly smooth horizontal table. The surfaces of the 12-kg block are rough, with   between the block and the table. If the 5.0-kg block accelerates downward when it is released, find its acceleration.

Accepted Answer

A)  1.0 m/s2 
B)  1.2 m/s2 
C)  1.4 m/s2 
D)  1.6 m/s2 
E)  1.8 m/s2 
A)  1.0 m/s2 
B)  1.2 m/s2 
C)  1.4 m/s2 
D)  1.6 m/s2 
E)  1.8 m/s2

Question 5

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

Accepted Answer

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

Question 6

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.

Accepted Answer

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 
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 7

Two boxes are connected by a weightless cord running over a very light frictionless pulley as shown in the figure. Box A, of mass 8.0 kg, is initially at rest on the top of the table. The coefficient of kinetic friction between box A and the table is 0.10. Box B has a mass of 15.0 kg, and the system begins to move just after it is released.   (a) Draw the free-body diagrams for each of the boxes, identifying all of the forces acting on each one.
(b) Calculate the acceleration of each box.
(c) What is the tension in the cord?

Accepted Answer

(a) Box A is acted on by the downward fo

Question 8

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?

Accepted Answer

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

Question 9

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

Accepted Answer

A)  True 
B)  False 
A)  True 
B)  False

Question 10

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?

Accepted Answer

(a) The following forces act on the 5.0-

Question 11

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?

Accepted Answer

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

Question 12

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.

Accepted Answer

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

Question 13

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

Accepted Answer

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

Question 14

Block A of mass 5.0 kg and block X are attached to a rope which passes over a pulley, as shown in the figure. An 80-N force P is applied horizontally to block A, keeping it in contact with a rough vertical face. The coefficients of static and kinetic friction between the wall and block A are μs = 0.40 and μk = 0.30. The pulley is light and frictionless. The mass of block X is adjusted until block A moves upward with an acceleration of 1.6 m/s2. What is the mass of block X?

Accepted Answer

A)  9.9 kg 
B)  9.3 kg 
C)  8.7 kg 
D)  8.1 kg 
E)  7.5 kg 
A)  9.9 kg 
B)  9.3 kg 
C)  8.7 kg 
D)  8.1 kg 
E)  7.5 kg

Question 15

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?

Accepted Answer

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

Question 16

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?

Accepted Answer

A)  T = m2g 
B)  T > m2g 
C)  T 2g 
D)  T = m1g 
E)  T > m1g 
A)  T = m2g 
B)  T > m2g 
C)  T 2g 
D)  T = m1g 
E)  T > m1g

Question 17

A system of blocks and a frictionless pulley is shown in the figure. Block A has a mass of 2.0 kg and is on a rough horizontal surface for which μs = 0.40 between the surface and block A. The rope pulls horizontally on block A. Block C has a mass of 1.0 kg. An external force P = 23.0 N, applied vertically to block A, maintains the system at rest as shown in the figure. What is the friction force on block A?

Accepted Answer

A)  6.3 N 
B)  6.9 N 
C)  7.5 N 
D)  5.7 N 
E)  5.1 N 
A)  6.3 N 
B)  6.9 N 
C)  7.5 N 
D)  5.7 N 
E)  5.1 N

Question 18

In the figure, two wooden blocks each of 0.30 kg mass are connected by a string that passes over a very light frictionless pulley. One block slides on a horizontal table, while the other hangs suspended by the string, as shown in the figure. At time t = 0, the suspended block is 0.80 m over the floor, and the blocks are released from rest. After 2.5 s, the suspended block reaches the floor. What is the coefficient of kinetic friction between the table and the sliding block?

Accepted Answer

A)  0.35 
B)  0.52 
C)  0.84 
D)  0.65 
E)  0.95 
A)  0.35 
B)  0.52 
C)  0.84 
D)  0.65 
E)  0.95

Question 19

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

Accepted Answer

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. 
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.

Question 20

A 4.00-kg box sits atop a 10.0-kg box on a horizontal table. The coefficient of kinetic friction between the two boxes and between the lower box and the table is 0.600, while the coefficient of static friction between these same surfaces is 0.800. A horizontal pull to the right is exerted on the lower box, as shown in the figure, and the boxes move together. What is the friction force on the UPPER box?

Accepted Answer

A)  19.3 N to the right 
B)  19.3 N to the left 
C)  23.5 N to the right 
D)  31.4 N to the right 
E)  31.4 N to the left 
A)  19.3 N to the right 
B)  19.3 N to the left 
C)  23.5 N to the right 
D)  31.4 N to the right 
E)  31.4 N to the left

Exam 7: Newtons Third Law

A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. During the collision

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

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 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 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?

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

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?

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.

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

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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