Question 1

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

Accepted Answer

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. 
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.

Question 2

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

Accepted Answer

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. 
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 3

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.

Accepted Answer

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

Question 4

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 5

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 6

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.

Accepted Answer

The answer of In a ballistics test,a 1.50-g bullet is...

Question 7

A 0.500-kg ball traveling horizontally on a frictionless surface approaches a very massive stone at 20.0 m/s perpendicular to wall and rebounds with 70.0% of its initial kinetic energy. What is the magnitude of the change in momentum of the stone?

Accepted Answer

A)  18.4 kg•m/s 
B)  14.0 kg•m/s 
C)  3.00 kg•m/s 
D)  1.63 kg•m/s 
E)  0.000 kg•m/s 
A)  18.4 kg•m/s 
B)  14.0 kg•m/s 
C)  3.00 kg•m/s 
D)  1.63 kg•m/s 
E)  0.000 kg•m/s

Question 8

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

Accepted Answer

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

Question 9

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

Accepted Answer

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. 
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

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.

Accepted Answer

(a)2.0 m/s² (b)The acceleration

Question 11

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).P is closest to

Accepted Answer

A)  25 N. 
B)  125 N. 
C)  187.5 N. 
D)  245 N. 
E)  1225 N. 
A)  25 N. 
B)  125 N. 
C)  187.5 N. 
D)  245 N. 
E)  1225 N.

Question 12

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

Accepted Answer

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. 
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 13

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 14

In the figure,two identical ideal massless springs have unstretched lengths of 0.25 m and spring constants of 700 N/m.The springs are attached to a small cube and stretched to a length L of 0.30 m as in Figure A.An external force P pulls the cube a distance D = 0.020 m to the right and holds it there.(See Figure B.)The external force P,that holds the cube in place in Figure B,is closest to

Accepted Answer

A)  28 N. 
B)  25 N. 
C)  21 N. 
D)  18 N. 
E)  14 N. 
A)  28 N. 
B)  25 N. 
C)  21 N. 
D)  18 N. 
E)  14 N.

Question 15

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

Accepted Answer

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. 
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 16

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.

Exam 8: Force

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

A 0.500-kg ball traveling horizontally on a frictionless surface approaches a very massive stone at 20.0 m/s perpendicular to wall and rebounds with 70.0% of its initial kinetic energy. What is the magnitude of the change in momentum of the stone?

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

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

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.

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).P is closest to

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

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 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 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

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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 pull P is closest to

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