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Chapter 7: Q21Q (page 170)
Why do you tend to lean backward when carrying a heavy load in your arms?
When you lean backward with a load in your arms, the center of mass becomes stable, and you are able to move forward without much difficulty.
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Suppose the force acting on a tennis ball (mass 0.060 kg) points in the \({\bf{ + x}}\) direction and is given by the graph of Fig. 7鈥�33 as a function of time.
(a) Use graphical methods (count squares) to estimate the total impulse given the ball.
(b) Estimate the velocity of the ball after being struck; assuming the ball is being served so it is nearly at rest initially. [Hint: See Section 6鈥�2.]
FIGURE 7-33 Problem 23.
A light object and a heavy object have the same kinetic energy. Which has the greater momentum? Explain.
An atomic nucleus of mass m traveling with speed v collides elastically with a target particle of mass 2m (initially at rest) and is scattered at 90掳.
(a) At what angle does the target particle move after the collision?
(b) What are the final speeds of the two particles?
(c) What fraction of the initial kinetic energy is transferred to the target particle?
A (lightweight) pallet has a load of ten identical cases of tomato paste (see Fig. 7鈥�39), each of which is a cube of length \(l\). Find the center of gravity in the horizontal plane, so that the crane operator can pick up the load without tipping it.
FIGURE 7-39
Problem 53.
Billiard balls A and B, of equal mass, move at right angles and meet at the origin of an xy coordinate system as shown in Fig. 7鈥�36. Initially ball A is moving along the y axis at \({\bf{ + 2}}{\bf{.0}}\;{\bf{m/s}}\), and ball B is moving to the right along the x axis with speed \({\bf{ + 3}}{\bf{.7}}\;{\bf{m/s}}\).After the collision (assumed elastic), ball B is moving along the positive y axis (Fig. 7鈥�36) with velocity What is the final direction of ball A, and what are the speeds of the two balls?
FIGURE 7-36
Problem 46. (Ball A after the Collison is not shown)
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