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- Thread starter nirgro
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It depends what the wall is made of.

- #3

Halc

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Two cars with a relative speed of 30 mph (I assume you mean mph and not miles) will each receive about the same impact (same short-duration change in velocity, same damage) as hitting a stationary immovable wall at 15 mph.

If on the other hand the cars are each moving at 30 mph in opposite directions (a relative speed of 60 mph), then they will each receive about the same impact as hitting the wall at 30 mph.

- #4

nirgro

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sorry not sure i got what you say

2 cars hit each other at the speed of 30 each one of them.its like one car hits the wall at 15??

isnt it like a car hit a wall at 60?

2 cars hit each other at the speed of 30 each one of them.its like one car hits the wall at 15??

isnt it like a car hit a wall at 60?

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- #5

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You might be losing this bet!sorry not sure i got what u say

2 cars hit each other at the speed of 30 each one of them.its like one car hits the wall at 15??

isnt it like a car hit a wall at 60?

- #6

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isnt it like a car hit a wall at 60?

It depends what the wall is made of.

It also depends on the crumple characteristics of the car. Your question is way too vague to have a solid answer.

- #7

nirgro

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why?

- #8

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If the wall is unbreakable and immovable, then hitting it at 30mph is the same as two cars hitting each other if both are doing 30mph. The impact on the car is the same: it stops dead from 30mph to zero with no forward motion.why?

- #9

If two cars, each with ##v_0 = 15\text{mph}## (i.e. approach speed ##2v_0 = 30\text{mph}##) hit each other, then each is still apportioned ##\frac{1}{2}m{v_0}^2## worth of deformation. This assuming symmetry, of course.

- #10

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Why WHAT? Which statement are you questioning?why?

- #11

nirgro

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so i lost the bet but still nice to know

thanks.

- #12

Mister T

Science Advisor

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Usually in a question like this we assume the time taken is the same in both cases, or at least about the same, so that it makes no difference. The damage is the same in both cases.

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