Question

A 200 g puck revolves in a circle on a frictionless table at the end of a 50 cm long string. The puck’s angular momentum about the center of the circle is 3.00 kg*m2/s. What is the tension in the string?

Answer 1

Angular momentum=I⍵=3.

I=mr²=0.2(0.5)²=0.2×0.25=0.05. So ⍵=3/0.05=60 rad/s.

The centrifugal force constraining the puck to circular motion is m⍵²r=0.2(3600)0.5=360N, which is the tension in the string. This is the same as L²/(mr³)=9/(0.2×0.5³) where L=3.