A ring and a disc having the same mass, roll without slipping with the same linear velocity. If the kinetic energy of the ring is 8 j , Find the kinetic energy of disc (in J)

Options

A. 2 J
B. 4 J
C. 6 J
D. 12 J

Answer

C

Explanation

`(KE_("disc"))/(KE_("ring"))=(1+(K^(2)//R^(2))_(d))/(1+(K^(2)//R^(2))_(r ))=(1+(1)/(2))/(1+1)=((3)/(2))/(2)`
`KE_("disc")=(3)/(4)xx KE_("ring")`
`= (3)/(4)xx(2)/(8) = 6 J`.