Calculating Distance Using Force, Mass, and Acceleration

Tags: acceleration, distance, force, mass
 P: 2 1. The problem statement, all variables and given/known data A rock is dropped from x(meters) height. The rock weighs 68 kg, and its force at impact with the ground is 15 kilonewtons. If the acceleration due to gravity is 9.8m/s^2, what is the distance/height the rock has fallen? 2. Relevant equations F=m*a 15kN=15000kg*m/s^2 666.4N=68kg*9.8m/s^2 The force exerted by the rock at stationary position is 666.4 Newtons. The rock fall distance is x meters. 3. The attempt at a solution 666.4N*x=15000N (666.4kg*m/s^2)*x=15000kg*m/s^2 x=(15000kg*m/s^2)/(666.4kg*m/s^2) x=22.51 This was all I could come with, but it is simply the ratio of the force. How do I find distance?
 Mentor P: 41,462 Please state the complete problem exactly as given. As you've written it, there's not enough information. (The impact force depends on the nature of the surface being hit.)
P: 153
 Quote by Doc Al Please state the complete problem exactly as given. As you've written it, there's not enough information. (The impact force depends on the nature of the surface being hit.)
Shouldn't there be a formula for the kinetic energy of a mass falling distance x and a formula for the F generated by an unknown kinetic energy when it hits? The two could then be equated resolving x.

I don't see elastic/inelastic collisions mentioned.

Mentor
P: 41,462
Calculating Distance Using Force, Mass, and Acceleration

 Quote by AC130Nav Shouldn't there be a formula for the kinetic energy of a mass falling distance x
That one's easy.
 and a formula for the F generated by an unknown kinetic energy when it hits?