A laboratory flywheel is mounted on a nearly frictionless vertical axle
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Torque and Rotational Dynamics · Torque and Rotational Dynamics
Problem
A laboratory flywheel is mounted on a nearly frictionless vertical axle. A student chooses counterclockwise (viewed from above) as the positive angular direction for all measurements that follow.
During a short test, the wheel is given a single push that causes it to rotate exactly 90∘ clockwise in 0.40s, after which it coasts without further external torques. The student’s electronic sensor records an average angular velocity of −3.9rads−1 during the push interval.
(a) State the sign (positive or negative) of the wheel’s angular displacement during the push interval and justify your answer using the student’s sign convention.
(b) Explain why the sensor reading of −3.9rads−1 is consistent with the observed rotational motion.
(c) Immediately after the push ends, the wheel’s angular velocity is measured to be −5.2rads−1. Describe—in words rather than numbers—the subsequent rotational motion of the wheel if a very small, constant kinetic friction torque acts opposite the wheel’s direction of motion. In your description, refer explicitly to the signs of angular velocity and angular acceleration.