CHAPTER 16

Rotational Motion

1 . A machine used to manufacture smartphone cases has a gear that rotates according to the following
equation: θ = 2.5 + 6.4t - 4.4t 2 . What is the angular acceleration of the gear at a time of 1s?
(A) –8.8 rad/s^2
(B) –4.4 rad/s^2
(C) –2.4 rad/s^2
(D) 4.5 rad/s^2
(E) 6.4 rad/s^2

2 . A child stands on a rotating platform at point A, as shown in the figure. The platform is rotating at a
constant rate of ω when the child begins walking along the radius of the platform to point B. Which of
the following statements explains the changes in the rotational velocity of the platform?
(A) The angular velocity will increase as predicted by conservation of angular momentum.
(B) The angular velocity will increase as predicted by conservation of energy.
(C) The angular velocity will remain the same as predicted by conservation of energy.
(D) The angular velocity will decrease as predicted by conservation of angular momentum.
(E) The angular velocity will decrease as predicted by conservation of kinetic energy.