Rolling and sliding sphere on flat surface

[versatilehong]

Homework Statement

In a laboratory experiment two spherical balls are launched on a °at surface. Both are
uniform spheres of radius R and mass m. They are both given the same amount of
initial kinetic energy K0. However:
-ball A rolls without slipping
-ball B slides without rotating
What is the ratio Vb/Va?

Homework Equations

Moment of inertia of solid sphere= 2/5 (mr^2)

The Attempt at a Solution

for the rotating, I did

KErolling=1/2 mv^2 = 1/2 Iw^2 => KEo = 7/10 mv^2

then for the slipping, I'm having a bit of problem. I am not sure if i have to include the friction force or not. Without friction, it'd be F=ma, then KEo=ma, I'm not sure if i can substitute KEo as F or not..

Thanks

 

[Doc Al]

Since B slides without rotating, the friction force must be zero.