A solid sphere of mass 5 kg rolls on a plane surfaces. Find its kinetic energy at an instant when its centre moves with speed 4 m/s .

Options

A. 56 J
B. 45 J
C. 75 J
D. 105 J

Answer

A

Explanation

As we know, the rotational kinetic energy of a body is given by,
`KE=1/2 mv^(2)[1+(k^(2))/(R^(2))]`
where, `k=` radius of gyration
Given, `m=5kg, v=4m//s` and `k=sqrt(2/5)R`
Hence, `KE=5/2xx4^(2)[1+2/5] rArr KE= 40 xx 7/5=56 J`
Hence, the correct option is (a).