# Newton's Second Law and car acceleration

• Annubes

#### Annubes

I'm having a hard time understanding this.
If a car that has a constant acceleration hits me let's say at 10km/h then at 100km/h will it exert the same amount of force on me? F= ma mass and acceleration are constant. But this doesn't seem right, does it?

Do you guys know any good website or a book that has questions that will test my conceptual understanding of Newton's laws.
Thanks:tongue2:

If you're talking about hitting, you have to consider momentum, which does take into account the velocity of the car.

The force accelerating the car is not the same as the force you'd experience when it hit you. F=ma works for the car, but the force you feel is the change in your momentum delta-P, divided by the time it takes to change momentum, delta-t.

Consider the case of a car that isn't accelerating at all, just moving at constant speed. When it hits you, there's no accelerating force F=ma, but you'll still feel a force on impact.

ahh... ok. I guess I have to wait till we get to momentum to fully understand this. thanks