TITLE: Force applied at the moment of hit
QUESTION [1 upvotes]: I have been thinking of this problem quite long time, but couldn't find the solution: 
Assume that we can measure only the velocity, v, of an object with mass, m, when it hits a rigid and stationary object. How can I calculate the amount of force applied by that hitting object? The applied force would increase from zero to its maximum and then decrease to zero during the hit. So, I am asking the maximum force.
On the other hand, I wonder if my assumption, which is only v can be measured at the moment of hit, was proper.

REPLY [1 votes]: Forces cause a change in momentum (or a change in velocity).  If you can only measure one velocity, you cannot tell how much the change is.
$$F \times \Delta t = m \times \Delta v$$
$$F =\frac{ m\times \Delta v}{\Delta t}$$
A ball that hits a floor and deforms a lot has a long interaction time.  A rock that hits a solid floor has a very short interaction time.  The forces are much greater for the rock because the time is short.  You could not tell the difference between them by measuring only one velocity.
{"set_name": "stack_exchange", "score": 1, "question_id": 136487}