Work/Energy
7 . Which of the following is a scalar?
(A) velocity
(B) acceleration
(C) displacement
(D) kinetic energy
(E) force8 . A 500-g block on a flat tabletop slides 2.0 m to the right. If the coefficient of friction between the
block and the table is 0.1, how much work is done on the block by the table?
(A) 0.5 J
(B) 1.0 J
(C) 0 J
(D) 100 J
(E) 50 J9 . A block has 1500 J of potential energy and 700 J of kinetic energy. Ten seconds later, the block has
100 J of potential energy and 900 J of kinetic energy. Friction is the only external force acting on the
block. How much work was done on this block by friction?
(A) 600 J
(B) 200 J
(C) 1400 J
(D) 1200 J
(E) 120 JMomentum
10 . Two identical small balls are moving with the same speed toward a brick wall. After colliding with
the wall, ball 1 sticks to the wall while ball 2 bounces off the wall, moving with almost the same
speed that it had initially. Which ball experiences greater impulse?
(A) ball 1
(B) ball 2
(C) Both experience the same impulse.
(D) The answer cannot be determined unless we know the time of collision.
(E) The answer cannot be determined unless we know the force each ball exerts on the wall.
11 . Ball A moves to the right with a speed of 5.0 m/s; Ball B moves to the left with speed 2.0 m/s. Both
balls have mass 1.0 kg. What is the total momentum of the system consisting only of balls A and B ?
(A) 7.0 N·s to the right
(B) 3.0 N·s to the right
(C) zero
(D) 7.0 N·s to the left
(E) 3.0 N·s to the left