Question

There object, `A` : (a solid sphere), `B` : (a thin circular disk) and `C` : (a circular ring), each have the same mass `M` and radius `R`. They all spin with the same angular speed `omega` about their own symmetry axes. The amount of work `(W)` required ot bring them to rest, would satisfy the relation
A. `W_A gt W_C gt W_B`
B. `W_C gt W_B gt W_A`
C. `W_B gt W_A gt W_C`
D. `W_A gt W_B gt W_C`

Answer 1

Correct Answer - B
(b) Using work energy theorem
`W = Delta K = (1)/(2) I omega^2`
`W prop I`
`W_A : W_B : W_C = (2)/(5) MR^2 : (1)/(2) MR^2 : MR^2`
`W_A : W_B : W_C = (2)/(5) : (1)/(2) : 1`
Hence `W_C gt W_B gt W_A`.