knightmoves wrote:builderguy135 wrote:v=sqrt(2gh)
This assumes you have a frictionless ball sliding down the ramp, and so all the gravitational potential energy is available for the kinetic energy of the center of mass. You don't, and it isn't. The ball rolls, and so some of the energy is converted to rotational energy instead.
d = v^2/g is fine, but setting 0.5mv^2 = mgh is not. When you include the rotational energy that the ball must have, your expression is 0.7mv^2 = mgh,
which gets you d = (1/0.7)h
Oh, that's probably right.