[Kleinrock]

A car moving at 100 km / hour, crashed into a concrete wall that doesn't move. How much time it takes to stop the car and how much its acceleration?

Nb: I think this question is not exhaustive, but maybe you have another ideas?

[smoothy]

Trick question... the decelleration G-forces will vary greatly by the vehicle... I.E. it will be a far higher number for a car built in the 60's with a strong frame, vs. a car built las year with very effective crumple zones that reduce the deceleration g-forces at impact via controlled deformation.

Unless there are assumptions being made for class... but in the real world what I said applies.

[Kleinrock]

Oh, I'm sorry.
I forgot to put something in the question. This is the complete question:

A car moving at 100 km / hour, crashed into a concrete wall that doesn't move. How much time it takes to stop the car and how much its acceleration?
(nb: Ignore the gravity force, air friction, and mass of the car.)

[ebaines]

Kleinrock - as smoothy hinted, it's impossible to answer this question without additional data. We need to know how much of the car of the car is crushed on impact. Since you don't know either time or acceleration, then y must know distance in order to apply one of the standard equations of motion, viz:



or

.