how much force would be exerted

Question

If he was not wearing his seatbelt the windshield would stop bobs head in about 0.001 seconds. How much force would be exerted on bobs head

Answer 1

You need more information to answer this question.  Suppose you knew the linear momentum of Bob's head just before it hit the windshield.  Call it p₁.  After hitting the windshield the final momentum is p₂.

 

The impulse is

 

I = p₂ - p₁ = 0 - p₁  [assumes head came to rest on the windshield]

 

I = FΔt

 

F = I/Δt = -p₁/Δt

 

Δt = 0.001 sec  [given]

 

But as you can see, we cannot give you a final number for F without more information, such as the initial momentum of the head, or both its mass and initial speed.  Please provide this data.  Also, note the I assumed the head came to a rest on the windshield.  If it bounced back, it would have non-zero final momentum, and that would have to be provided in the problem statement, or at least sufficient data to compute it.