Ap Physics Worksheet With Answers (Page 8 of 8) in pdf

Ap Physics Worksheet With Answers Page 8

57. A solid rubber ball, of radius 1.2 cm and mass 0.50 kg, rolls on a flat surface. Its angular velocity is 4.0 rad/s. What is the ball’s

rotational kinetic energy?

I = 2/5 mr

= 2/5(0.50 kg)(0.012 m)

= 0.0000288 kg•m

Ek = ½ Iω

= ½(0.0000288 kg•m

)(4.0 rad/s)

= 0.0000576 J

58. Gina rolls a bowling ball of mass 7 kg and radius 10.9 cm down a lane with a velocity of 6 m/s. (a) Find the rotational kinetic

energy of the bowling ball, assuming it does not slip. (b) Find the total kinetic energy of the bowling ball.

(a) To find the rotational kinetic energy of the bowling ball, you need to know its moment of inertia and its angular velocity.

Assume the bowling ball is a solid sphere to find its moment of inertia.

Next, find the ball’s angular velocity.

Finally, solve for the rotational kinetic energy of the bowling ball.

(b) The total kinetic energy is the sum of the translational kinetic energy and the rotational kinetic energy of the bowling ball.

59. Angelina spins on a rotating pedestal with an angular velocity of 8 rad/s.. Bob throws her an exercise ball, which increases her

moment of inertia from 2 kg·m

to 2.5 kg·m

. What is Angelina’s angular velocity after catching the exercise ball? (Neglect any

external torque from the ball.)

Since there are no external torques, you know that the initial spin angular momentum must equal the final spin angular

momentum, and can therefore solve for Angelina’s final angular velocity:

Ap Physics Worksheet With Answers Page 8