Question

A disc of radius `0.5 m` is rotating about an axis passing through its centre and perpendicular to its plane. A tangential force of `2000 N` is applied to bring the dics to rest `2 s`. Calculate its abgular momentum.

Answer 1

Here, `r = 0.5m, F = 2000N, t = 2 s`
Final angular momentum, `L_(2) = 0`,
Initial angular momentum, `L_(1) = ?`
torque applied, `tau = - F xx r = - 2000 xx 0.5`
`= - 1000 N-m`
As `tau= (L_(2) - L_(1))/(t)`
`:. - 1000 = (0 - L_(1))/(2), L_(1) = 2000 kg m^(2) s^(-1)`