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Chapter 1: Q2DQ (page 123)
A ball thrown straight up has zero velocity at its highest point. Is the ball in equilibrium at this point? Why or why not?
The ball is not in equilibrium, at all moments during the motion as the gravitational force still acts on the ball.
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A shaft is drilled from the surface to the center of the earth (see Fig. 13.25). As in Example 13.10 (Section 13.6), make the unrealistic assumption that the density of the earth is uniform. With this approximation, the gravitational force on an object with mass m, that is inside the earth at a distance r from the center, has magnitude (as shown in Example 13.10) and points toward the center of the earth. (a) Derive an expression for the gravitational potential energyof the object鈥揺arth system as a function of the object鈥檚 distance from the center of the earth. Take the potential energy to be zero when the object is at the center of the earth. (b) If an object is released in the shaft at the earth鈥檚 surface, what speed will it have when it reaches the center of the earth?
A cube 5.0 cm on each side is made of a metal alloy. After you drill a cylindrical hole 2.0 cm in diameter all the way through and perpendicular to one face, you find that the cube weighs 6.30 N. (a) What is the density of this metal? (b) What did the cube weigh before you drilled the hole in it?
The acceleration of a particle is given by . (a) Find the initial velocitysuch that the particle will have the same x-coordinate atas it had at. (b) What will be the velocity at?
A shower head has 20 circular openings, each with radius 1.0 mm. The shower head is connected to a pipe with radius 0.80 cm. If the speed of water in the pipe is 3.0 m/s, what is its speed as it exits the shower-head openings?
Starting from the front door of a ranch house, you walk 60.0 m due east to a windmill, turn around, and then slowly walk 40.0 m west to a bench, where you sit and watch the sunrise. It takes you 28.0 s to walk from the house to the windmill and then 36.0 s to walk from the windmill to the bench. For the entire trip from the front door to the bench, what are your (a) average velocity and (b) average speed?
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