Conceptual Physics

with respect to the ground. (a) What is the total mass of the cat, the skateboard, and any remaining books? (b) What mass

book must she now throw at 15.0 m/s with respect to the ground to move at í2.00 m/s?

(a) kg

(b) kg

5.5 Stevie stands on a rolling platform designed for moving heavy objects. The platform has mass of 76 kg and is on a flat floor,
supported by rolling wheels that can be considered to be frictionless. Stevie's mass is 43 kg. The platform and Stevie are
stationary when she begins walking at a constant velocity of +1.2 m/s relative to the platform. (a) What is the platform's
velocity relative to the floor? (b) What is Stevie's velocity relative to the floor?
(a) m/s
(b) m/s

Section 8 - Collisions

8.1 A steel ball of mass 0.76 kg strikes a brick wall

in an elastic collision. Incoming, it strikes the

wall moving 63° directly above a line normal

(perpendicular) to the wall. It rebounds off the

wall at an angle of 63° directly below the

normal line. The ball's speed is 8.4 m/s

immediately before and immediately after the

collision, which lasts 0.18 s. What is the

magnitude of the average force exerted by the

ball on the wall?

N

8.2 A quarterback is standing stationary waiting to make a pass when he is tackled from behind by a linebacker moving at

4.75 m/s. The linebacker holds onto the quarterback and they move together in the same direction as the linebacker was

moving, at 2.60 m/s. If the linebacker's mass is 143 kg, what is the quarterback's mass?

kg

Section 9 - Sample problem: elastic collision in one dimension

9.1 Two balls collide in a head-on elastic collision and rebound in opposite directions. One ball has velocity 1.2 m/s before the

collision, and í2.3 m/s after. The other ball has a mass of 1.1 kg and a velocity of í4.2 m/s before the collision. (a) What is the

mass of the first ball? (b) What is the velocity of the second ball after the collision?

(a) kg

(b) m/s

9.2 Two identical balls collide head-on in an elastic collision and rebound in opposite directions. The first ball has speed 2.3 m/s

before the collision and 1.7 m/s after. What is the speed of the second ball (a) before and (b) after the collision?

(a) m/s

(b) m/s

9.3 A 4.3 kg block slides along a frictionless surface at a constant velocity of 6.2 m/s in the positive direction and collides head-on

with a stationary block in an elastic collision. After the collision, the stationary block moves at 4.3 m/s. (a) What is the mass of

the initially stationary block? (b) What is the velocity of the first block after the collision?

(a) kg

(b) m/s

9.4 Ball A, which has mass 23 kg, is moving horizontally left to right at +7.8 m/s when it overtakes the 67 kg ball B, which is

moving left to right at +4.7 m/s, and they collide elastically. (a) What is ball A's velocity after the collision? (b) What is ball B's

velocity?

(a) m/s

(b) m/s

Section 12 - Interactive problem: shuffleboard collisions

12.1 Use the information given in the interactive problem in this section to determine the initial velocity of the blue puck that will

cause the red puck to stop at the scoring line. Test your answer using the simulation.

m/s

Copyright 2007 Kinetic Books Co. Chapter 7 Problems^163