Newton's Second Law finding value of force problem

[goomer]

Homework Statement

If a soccer ball of mass 0.5 kg is kicked with a speed of 14 m/s and hits a rock and is in contact with it for 0.18 seconds, with what force will it hit?

Homework Equations

F_net = ma

The Attempt at a Solution

I have no idea what to do to get the acceleration for the above formula. It can't possibly be just 14/0.18 can it?

 

[Infinitum]

Force can also be defined in terms of momentum and time. What is it, and can you use that in this problem?

 

[goomer]

Oh I see, so:

Force = Momentum/Time

Momentum = Mass * Velocity = 0.5 kg * 14 m/s = 7

Force = 7/0.18 s = 38.9N right?

 

[Infinitum]

Oh I see, so:

Force = Momentum/Time

Momentum = Mass * Velocity = 0.5 kg * 14 m/s = 7

Force = 7/0.18 s = 38.9N right?

Yep!

Force is actually the change in momentum per unit time. But since the ball was in contact with the stone for that time, and its velocity was zero then, your equation worked out.

 

[goomer]

Thank you so much for your help!