Which has a greater impact of force?

[preluderacer]

Homework Statement

Consider two less-than-desirable options. In the first you are driving 30 miles/hr and crash head-on into an identical car also going 30 miles/hr. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greatest impact force?

The Attempt at a Solution

Im thinking they are the same because both collisions are totally inelastic?

 

[dacruick]

would you rather run into a stationary wall or run into a wall moving towards you at 30 mph?

 

[housemartin]

well, actually take a look at impulse ;] you can rewrite it as:
(change in momentum) = (Force) * (time of action)
change in momentum is the same for both cases, time is too, so...? ;]

 

[dacruick]

well, actually take a look at impulse ;] you can rewrite it as:
(change in momentum) = (Force) * (time of action)
change in momentum is the same for both cases, time is too, so...? ;]

wouldn't your time of impact be halved by the fact that the other car is moving towards you as well?

 

[housemartin]

it is more complicated in real life i guess, but here problem statement said: "the collision time is the same in both cases"
EDIT: besides you can use Newton's third law here: action equals reaction. So the car will extend same force on other identical car or standing wall.

 

[dacruick]

it is more complicated in real life i guess, but here problem statement said: "the collision time is the same in both cases"

right you are, I apologize. Although that's a stupid question, usually physics teachers use the student's intuition for their benefit, not to confuse them.