Question 1

A 450-kg sports car accelerates from rest to 100 km/h in 4.80 s. What magnitude force does a 68.0 kg passenger experience during the acceleration?

Accepted Answer

A)  311 N 
B)  342 N 
C)  82.0 N 
D)  394 N 
A)  311 N 
B)  342 N 
C)  82.0 N 
D)  394 N

Question 2

The figure shows an object's acceleration-versus-force graph. What is the mass of this object?

Accepted Answer

A)   2.5 g 
B)   400,000 g 
C)   1.6 g 
D)   630 g 
A)   2.5 g 
B)   400,000 g 
C)   1.6 g 
D)   630 g

Question 3

An astronaut weighs 99 N on the Moon, where the acceleration of gravity is 1.62 m/s². How much does she weigh on Earth?

Accepted Answer

A)  99 N 
B)  61 N 
C)  600 N 
D)  440 N 
E)  16 N 
A)  99 N 
B)  61 N 
C)  600 N 
D)  440 N 
E)  16 N

Question 4

Two forces act on a 55-kg object. One force has magnitude  65 N  directed   clockwise from the positive  x -axis, and the other has a magnitude  35 N at   clockwise from the positive  y -axis. What is the magnitude of this object's acceleration?

Accepted Answer

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

Question 5

A net force of 125 N is applied to a certain object. As a result, the object accelerates with an acceleration of 24.0 m/s². The mass of the object is

Accepted Answer

A)  5.21 kg. 
B)  2880 kg. 
C)  144 kg. 
D)  0.200 kg. 
E)  3000 kg. 
A)  5.21 kg. 
B)  2880 kg. 
C)  144 kg. 
D)  0.200 kg. 
E)  3000 kg.

Question 6

When a 45-kg person steps on a scale in an elevator, the scale reads a steady 410 N. Which of the following statements must be true? (There could be more than one correct choice.)

Accepted Answer

A)  The elevator is accelerating downward at a constant rate. 
B)  The elevator is moving downward at a constant rate. 
C)  The elevator is accelerating upward at a constant rate. 
D)  The elevator is moving upward at a constant rate. 
E)  From the given information, we cannot tell if the elevator is moving up or down. 
A)  The elevator is accelerating downward at a constant rate. 
B)  The elevator is moving downward at a constant rate. 
C)  The elevator is accelerating upward at a constant rate. 
D)  The elevator is moving upward at a constant rate. 
E)  From the given information, we cannot tell if the elevator is moving up or down.

Question 7

During a hard stop, a car and its passengers slow down with an acceleration o   What magnitude force does a 50-kg passenger exert on the seat belt in such a stop?

Accepted Answer

The answer of During a hard stop, a car and...

Question 8

An object is being acted upon by three forces and as a result moves with a constant velocity. One force is  60.0 N  along the  +x -axis, and the second is  75.0 N along the  +y -axis. What is the magnitude of the third force?

Accepted Answer

A)   48.0 N 
B)   15.0 N 
C)   67.5 N 
D)   135 N 
E)   96.0 N 
A)   48.0 N 
B)   15.0 N 
C)   67.5 N 
D)   135 N 
E)   96.0 N

Question 9

Inside of a train a ball of weight W is hanging by a light wire at rest from the ceiling. The wire makes an angle θ with the ceiling, as shown in the figure. Which one of the following conditions
Must be true about the tension T in the wire?

Accepted Answer

A)  $T \tan \theta = W$ 
B)  $T \cos \theta = W$ 
C)  T = W 
D)  T = ma 
E)  $T \sin \theta = W$ 
A)  $T \tan \theta = W$ 
B)  $T \cos \theta = W$ 
C)  T = W 
D)  T = ma 
E)  $T \sin \theta = W$

Question 10

The figure shows an acceleration-versus-force graph for three objects pulled by wires. If the mass of object 2 is 36 kg, what are the masses of objects 1 and 3?

Accepted Answer

A)   90 kg and  12 kg 
B)   12 kg  and  72 kg 
C)   72 kg  and  18 kg 
D)   12 kg  and  90 kg 
A)   90 kg and  12 kg 
B)   12 kg  and  72 kg 
C)   72 kg  and  18 kg 
D)   12 kg  and  90 kg

Question 11

A horizontal 52-N force is needed to slide a 50-kg box across a flat surface at a constant velocity of 3.5 m/s. What is the coefficient of kinetic friction between the box and the floor?

Accepted Answer

A)  0.11 
B)  0.10 
C)  0.09 
D)  0.13 
A)  0.11 
B)  0.10 
C)  0.09 
D)  0.13

Question 12

Two boxes are connected to each other by a string as shown in the figure. The  10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension  T  in the string?

Accepted Answer

A)   T30 N 
E)   T=30 N 
A)   T30 N 
E)   T=30 N

Question 13

Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which
One of the following statements about these objects is correct?

Accepted Answer

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

Question 14

The figure shows a system consisting of three blocks, a light frictionless pulley, and light
connecting ropes that act horizontally on the upper two blocks. The 9.0-kg block is on a
perfectly smooth horizontal table. The surfaces of the 12-kg block are rough, with µk =
0.30 between the 12-kg and 9.0-kg blocks. The mass M of the hanging block is set so that it
descends at a constant velocity of 3.25 m/s.
(a) What is the mass M of the hanging block?
(b) The mass M is now changed to 5.0 kg, causing it to accelerate downward after it is
released. What is the acceleration of the hanging mass?

Accepted Answer

(a) 3.6 kg

Question 15

Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to
The right, and both weigh the same.   Which of the figures below shows a correct free-body diagram of the horizontal forces acting on
The upper block, A?

Accepted Answer

A)   
B)  
(No horizontal forces act on $A$.) 
C) $A \longrightarrow 50 \mathrm {~N}$ 
D) $\mathrm{A} \longrightarrow 100 \mathrm{~N}$ 
E)   
A)   
B)  
(No horizontal forces act on $A$.) 
C) $A \longrightarrow 50 \mathrm {~N}$ 
D) $\mathrm{A} \longrightarrow 100 \mathrm{~N}$ 
E)

Question 16

A 50-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the
Surface is 0.40, and the coefficient of kinetic friction is 0.30. What is the force of friction on the box?

Accepted Answer

A)  250 N 
B)  32 N 
C)  200 N 
D)  220 N 
E)  620 N 
A)  250 N 
B)  32 N 
C)  200 N 
D)  220 N 
E)  620 N

Question 17

A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0° on either side of the vertical direction. What is the tension in each cable?

Accepted Answer

A)  2560 N 
B)  231 N 
C)  400 N 
D)  800 N 
E)  3920 N 
A)  2560 N 
B)  231 N 
C)  400 N 
D)  800 N 
E)  3920 N

Question 18

A 75-N box rests on a perfectly smooth horizontal surface. The minimum force need to start the box moving is

Accepted Answer

A)  75 N. 
B)  750 N. 
C)  7.5 N. 
D)  any horizontal force greater than zero. 
A)  75 N. 
B)  750 N. 
C)  7.5 N. 
D)  any horizontal force greater than zero.

Question 19

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a very light rope that goes over an ideal pulley. If the masses are gently released, what is the resulting acceleration of the
Masses?

Accepted Answer

A)  0.00 m/s² 
B)  2.5 m/s² 
C)  6.1 m/s² 
D)  4.9 m/s² 
E)  3.7 m/s² 
A)  0.00 m/s² 
B)  2.5 m/s² 
C)  6.1 m/s² 
D)  4.9 m/s² 
E)  3.7 m/s²

Question 20

A very light wire is used to hang a series of  8.0-kg bricks. This wire will break if the tension in it exceeds  450 N. The bricks are hung one below the other from a hook in the ceiling using this wire, as shown in the figure.
(a) How many whole bricks can be hung without breaking the wire?
(b) If you add one more brick to the number found in part (a), which string will break?

Accepted Answer

(a) 5 (b)

Exam 4: Dynamics: Newtons Laws of Motion

A 450-kg sports car accelerates from rest to 100 km/h in 4.80 s. What magnitude force does a 68.0 kg passenger experience during the acceleration?

The figure shows an object's acceleration-versus-force graph. What is the mass of this object?

An astronaut weighs 99 N on the Moon, where the acceleration of gravity is 1.62 m/s². How much does she weigh on Earth?

Two forces act on a 55-kg object. One force has magnitude 65 N directed clockwise from the positive x -axis, and the other has a magnitude 35 N at clockwise from the positive y -axis. What is the magnitude of this object's acceleration?

A net force of 125 N is applied to a certain object. As a result, the object accelerates with an acceleration of 24.0 m/s². The mass of the object is

When a 45-kg person steps on a scale in an elevator, the scale reads a steady 410 N. Which of the following statements must be true? (There could be more than one correct choice.)

During a hard stop, a car and its passengers slow down with an acceleration o What magnitude force does a 50-kg passenger exert on the seat belt in such a stop?

An object is being acted upon by three forces and as a result moves with a constant velocity. One force is 60.0 N along the +x -axis, and the second is 75.0 N along the +y -axis. What is the magnitude of the third force?

Inside of a train a ball of weight W is hanging by a light wire at rest from the ceiling. The wire makes an angle θ with the ceiling, as shown in the figure. Which one of the following conditions Must be true about the tension T in the wire?

The figure shows an acceleration-versus-force graph for three objects pulled by wires. If the mass of object 2 is 36 kg, what are the masses of objects 1 and 3?

A horizontal 52-N force is needed to slide a 50-kg box across a flat surface at a constant velocity of 3.5 m/s. What is the coefficient of kinetic friction between the box and the floor?

Two boxes are connected to each other by a string as shown in the figure. The 10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension T in the string?

Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which One of the following statements about these objects is correct?

A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0° on either side of the vertical direction. What is the tension in each cable?

A 75-N box rests on a perfectly smooth horizontal surface. The minimum force need to start the box moving is

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a very light rope that goes over an ideal pulley. If the masses are gently released, what is the resulting acceleration of the Masses?

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