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The problem:

In a car crash, a passenger with a mass of 82kg is not wearing a seatbelt. The car is travelling at 45km per hour. What impulse must the car's airbag provide in order to stop the passenger's motion?

Explain why hitting an airbag will cause less injury than if a passenger hits the dashboard.

Here is what I did:

I thought impulse meaning force, so to find force I can use $F = m\Delta v/\Delta t$. But I don't know what $t$ is. How can I find $t$?

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up vote 2 down vote accepted

Impulse is the product of the force and the time over which it is applied, and tells you the total change in momentum: $$I = F\Delta t = \Delta p$$.

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