Question

Two ponies of equal mass are initially at diametrically opposite points on the rim of a large horizontal turntable that is turning freely on a vertical, frictionless axle through its center. The ponies simultaneously start walking toward each other across the turntable. As they walk, what happens to the angular speed of the turntable? (A) It increases(B) It decreases(C) It stays constantConsider the ponies-turntable system in this process is the angular momentum of the system conserved?(A) Yes(B) No

Answer 1

Answer:A

Explanation:

Given

Two ponies are at Extreme end of turntable with mass m

suppose turntable is moving with angular velocity $\omega$

Moment of inertia of Turntable and two ponies

$I=I_o+2mr_0^2$

let say at any time t they are at a distance of r from center such $r$

Moment of inertia at that instant

$I'=I_0+2mr'^2$

$I'$

conserving angular momentum as net Torque is zero

$I\omega =I'\omega '$

$\omega '=\frac{I}{I'}\times \omega$

$\omega '>\omega$

Thus we can say that angular velocity increases as they move towards each other.