Question

Two wheels A and B are mounted on the same axle. Moment of inertia of A is 6 kg `m^(2)` and is rotated at 600 rpm, when B is at rest. What will be moment of inertia of B, if their combined speed is 400 rpm?
A. `8 kg m^(2)`
B. `12 kg m^(2)`
C. `3 kg m^(2)`
D. `5 kg m^(2)`

Answer 1

Correct Answer - C
Applying the principle of conservation of angular momentum.
`(I_(1)+I_(2))omega = I_(1)omega_(1)+I_(2)omega_(2)`
`(6+I_(2))xx(400)/(60)xx2pi=6xx(600)/(60)xx2pi + I_(2)xx0`
`6+I_(2)=(36)/(4)=9 therefore I_(2)=3 kg m^(2)`