Question

How would a spinning disk's kinetic energy change if its moment of inertia were five times larger but its angular speed were five times smaller? 

 0.1 times as large as before 

 10 times as large as before 

 5 times as large as before 

 same as before 

 0.2 times as large as before

Answer 1

Rotational K.E = 0.5*I*w^2

I= moment of inertia

and w= angular speed

when I' = 5*I

and w' = w / 5

=> K.E ' = 0.5 *5*I*(w/5)^2

=> K.E ' = 0.2 * (0.5*I*w^2)

=> K.E ' = 0.2 K.E hence option (E) ans...