A 2200-kg sport utility vehicle traveling at 86 km/h can be stopped in 0.16 s if

Question

A 2200-kg sport utility vehicle traveling at 86 km/h can be stopped in 0.16 s if it hits a concrete wall. Assume a 60 kgperson was in the car that hit this wall. The velocity of theperson equals that of the car both before and after the crash, andthe velocity changes in 0.16 s. (a) What is the average force exerted on theperson?
______________ N (in a direction opposite to the initialmotion)

(b) Some people think that they can stop themselves rushing forwardby putting their hands on the dashboard. Find the mass of theobject that has a weight equal to the force you justcalculated.
________________kg
(a) What is the average force exerted on theperson?
______________ N (in a direction opposite to the initialmotion)

(b) Some people think that they can stop themselves rushing forwardby putting their hands on the dashboard. Find the mass of theobject that has a weight equal to the force you justcalculated.
________________kg

Explanation / Answer

This is an impulse question - impulse is defined as the timeintegral of force, or, more simply, just a change inmomentum. This formula will be useful: mv = Ft The only thing we have to do first is convert the speed giveninto meters per second: 86km x 1000m x 1h      = 23.8m/s 1h        1km     3600s We're looking for the force, and all the other information isalready given, so we just plug in numbers: F = mv = (60)(0-23.8) =8958N (in the direction opposite to motion)        t          0.16 b) If an object has a weight of 8958N, its mass is simplygiven by m = F/g = 8958/9.81 = 913kg (finalanswer)

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