Chapter 14: Work, Energy, and Power

A gear with a mass moment of inertia of 0.45 kg·m2 has a kinetic energy of rotation of 21 joules. What is its speed of rotation in rpm?

 

92.3 rpm

 

· 14-63

 

Wheel A in Figure P14–63 weighs 200 lb and has a radius of gyration of 2 ft. If the system is initially at rest, determine the angular velocity of A after B has dropped 8 ft. 

 

 

 

· 14-64

 

Masses A and B in Figure P14–64 are fastened together by a belt over pulley D. (Assume no slipping of the belt.) The mass moment of inertia of pulley D is 15 kg·m2. How far does mass B drop before reaching a velocity of 2 m/s? The system is initially at rest.

 

 

 

1.07 m

 

Chapter 15:  Impulse and Momentum

 

· Section: Problems

 

· 15-11

 

Determine the force required to bring an 8-ton truck traveling at 50 mph to rest in 5 seconds. How far does it travel?

 

7290 lb 183 ft

 

· 15-17

 

The rotor of an electric motor turns at 1750 rpm, weighs 150 lb, and has a radius of gyration of 9.5 in. Determine (a) the angular momentum at 1750 rpm and (b) the torque required to slow the rotor to 800 rpm in 2 seconds.

 

535 lb-s 145 lb-ft

 

· 15-32

 

A 4-kg rifle firing an 8-g bullet at 650 m/s obeys the law of conservation of momentum. Determine the recoil speed of the rifle.

 

1.3 m/s

 

· 15-43

 

Disc A in Figure P15–43 (IC = 8 kg · m2), while rotating at 100 rpm, is lowered onto disc B (IC = 10.5 kg · m2), causing the latter to rotate from rest. Assume no slipping and determine the angular velocity of B.

Chapter 14: Work, Energy, and Power

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