# Work, Energy, and Power

Work, Energy, and Power

14–56.

A gear with a mass moment of inertia of 0.45 kgm2 has a kinetic energy of rotation of 21 joules. What is its speed of rotation in 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 kgm2. How far does mass B drop before reaching a velocity of 2 m/s? The system is initially at rest.

Impulse and Momentum

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?

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.

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.

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.