A disc of mass 100 g and radius 10 cm has a projection on its circumference. The mass of projection is negligible. A 20 g bit of putty moving tangential to the disc with a velocity of 5 m s−1 strikes the projection and sticks to it. The angular velocity of disc is
In this case, the angular momentum of bit of putty about the axis of rotation = angular momentum of system of disc and bit of putty about the axis of rotation.
Let:
M = Mass of puty
m = Mass of disc
∴MvR=(mR22+MR2)ω
ω=MvR(mR22+MR2)
Putting all the values
ω=14.298 m/s