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Here is the problem: An impulse of 90 N times s is delivered by an average force of 1800 N. How long does the force act?

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Use the impulse formula, rearranged for the unknown, in SI units.

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Formula: impulse.

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Rearrange for time interval deltat.

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Substitute the known values.

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So the answer is time interval deltat equals 0.05 s.

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Impulse equals the change in momentum (impulse–momentum theorem). Spreading the same change in momentum over a longer time, as airbags and crumple zones do, reduces the average force.

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Substituted every value back into the formula: both sides agree, which checks out.