Question

To throw a discus, the thrower holds it with a fully outstretched arm. Starting from rest, he begins to turn with a constant angular acceleration, releasing the discus after making one complete revolution. The diameter of the circle in which the discus moves is about 1.8 m. If the thrower takes 1.0 s to complete one revolution, starting from rest, what will be the speed of the discus at release?

Answer 1

Starting from rest, a discus thrower releases the discus after making one complete revolution. Calculate angular acceleration and the speed of the discus at the instant of release by using rotational kinematics.

The diameter of the circle, the thrower moves is

Radius of the circular path,

Convert one complete revolution from revolution to radian:

Use the rotational kinematic equation to find the acceleration.

Here, is angular displacement, is initial angular velocity, is angular acceleration, and is time interval.

Rearranging the equation for angular acceleration

Substitutefor, zero for, and for t

Now, find the final angular velocity after using rotational kinematic equation.

Substitute zero for, and for t, and for

The relation between linear velocity and angular velocity is,

Thus, the speed of the discus at the release after rounding off to two significant digits is