# Does mass matter at all for kinematics vertical questions w/o friction?

This is the specific question w/o information on mass given, I think here is not enough info.

A block and a sphere are each released from rest at the top of an incline from the same height. The block slides with negligible friction while the sphere rolls without slipping. Compare the speed of the block at the bottom of the incline to the speed of the sphere at the bottom of the incline and explain the reasoning for that comparison.

Doesn’t mass matter so there is not enough information? Normally, you would use conservation of energy, but the problem is that they start out with different potential energies, depending on the mass (which we are not given).

Also, on the side of semantics, is it even possible to compare “speed” without specifying translational or rotational? You could do both, but not a general “speed” in my understanding.

For each object for energy conservation you will have $$\Delta\text{KE}=-\Delta\text{PE}$$. Since both of these terms are directly proportional to the mass, the mass variables on each side of the equation will cancel out. Therefore, you do not need to know the mass of each object to solve this problem.