Name: ___________________________________    Date: ______________



1.
A man wishes to pull a crate 15 m across a rough floor by exerting a force of 100 N. The coefficient of kinetic friction is 0.25. For the man to do the most work, the angle between the force and the horizontal should be:
A.
0
B.
14°
C.
43°
D.
66°
E.
76°


2.
The velocity of a particle moving along the x axis changes from vi to vf. For which values of vi and vf is the total work done on the particle positive?
A.
vi = 5m/s, vf = 2m/s
B.
vi = 5m/s, vf = –2m/s
C.
vi = –5m/s, vf = –2m/s
D.
vi = –5m/s, vf = 2m/s
E.
vi = –2m/s, vf = –5m/s


3.
Two objects interact with each other and with no other objects. Initially object A has a speed of 5 m/s and object B has a speed of 10 m/s. In the course of their motion they return to their initial positions. Then A has a speed of 4 m/s and B has a speed of 7 m/s. We can conclude:
A.
the potential energy changed from the beginning to the end of the trip
B.
mechanical energy was increased by nonconservative forces
C.
mechanical energy was decreased by nonconservative forces
D.
mechanical energy was increased by conservative forces
E.
mechanical energy was decreased by conservative forces


4.
A block is released from rest at point P and slides along the frictionless track shown. At point Q, its speed is:
A.
B.
2g(h1 – h2)
C.
(h1 – h2)/2g
D.
E.
(h1 – h2)2/2g


5.
Given a potential energy function U(x), the corresponding force is in the positive x direction if:
A.
U is positive
B.
U is negative
C.
U is an increasing function of x
D.
U is a decreasing function of x
E.
it is impossible to obtain the direction of from U


6.
A light rope passes over a light frictionless pulley attached to the ceiling. An object with a large mass is tied to one end and an object with a smaller mass is tied to the other end. Starting from rest the heavier object moves downward and the lighter object moves upward with the same magnitude acceleration. Which of the following statements is true for the system consisting of the two objects?
A.
The center of mass remains at rest.
B.
The net external force is zero.
C.
The velocity of the center of mass is a constant.
D.
The acceleration of the center of mass is g, downward.
E.
None of the above statements are true.


7.
A particle moves along the x axis. Its momentum is graphed below as a function of time. Rank the numbered regions according to the magnitude of the force acting on the particle, least to greatest.
A.
1, 2, 3, 4
B.
2, 3, 4, 1
C.
1, 4, 3, 2
D.
1, 3, 4, 2
E.
2, 4, 3, 1


8.
A rifle of mass M is initially at rest but free to recoil. It fires a bullet of mass m and velocity v (relative to the ground). After firing, the velocity of the rifle (relative to the ground) is:
A.
–mv
B.
–Mv/m
C.
–mv/M
D.
–v
E.
mv/M


9.
Two carts (A and B), having spring bumpers, collide as shown. Cart A has a mass of 2 kg and is initially moving to the right. Cart B has a mass of 3 kg and is initially stationary. When the separation between the carts is a minimum:
A.
cart B is still at rest
B.
cart A has come to rest
C.
the carts have the same momentum
D.
the carts have the same kinetic energy
E.
the kinetic energy of the system is at a minimum


10.
At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s. They move along nearby lines and pass without colliding. At the end of 2.0 s the acceleration of the center of mass of the two-ball system is:
A.
0.25g
B.
0.50g
C.
0.75g
D.
g
E.
g/0.75


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