Impact force exerted on a rolling wheel drop from a height

[MechaMZ]

Homework Statement

[PLAIN]http://img87.imageshack.us/img87/9964/impactforceonbike.png

A roller is rolling with a constant speed before and after the drop. How do i figure out the impact force exerted on the wheel when it just touch the floor from a height h?

Assume, angular velocity before and after dropping are equal, time taken (t) for the dropping motion, height (h=d), mass (m) are measured and known. Final vertical velocity is zero.

The Attempt at a Solution

in the scenario, i need to determine the impact force (F). however, the initial velocity is an unknown since I've no idea how to determine it. I've tried to let initial vertical velocity as:

V_i=V_{center of mass}= r x w

However, i think it should not the right way as assume V_i=V_{center of mass} because the motion of rolling and the vertical velocity are 90 degree.

So how do i actually determine the initial vertical velocity in order to find out my impact force exerts on vertical direction?

thank you so much for your patience and help.

 

[MechaMZ]

or i should use an energy conservation method?