In a particular crash test, a car of mass 1,500 kg collides with a wall as shown

Question

In a particular crash test, a car of mass 1,500 kg collides with a wall as shown in the figure. The initial and final velocities of the car are vi = -17.5i m/s and vf = 1.55i m/s, respectively. If the collision lasts 0.185 s, find the impulse caused by the collision and the average force exerted on the car.

I = 28575i kg m/s

average force exerted by the wall on the car = 154459.5 N

Now in real life, this automobile is cruising at 16.5 m/s (equal to 59.4 km/hr) when it is about to hit a pedestrian stuck in the middle of the road. The super hero Mr. Incredible comes to the rescue. He does not want to get sued, however. Therefore, he will not push the car with a force greater than 5.0 x 104 N, otherwise, the bumper will get damaged. How much time does he need to stop this car?

____ s

Explanation / Answer

Force applied x t = change in car's momentum

F x t = m.v ..
F = 5.0*10^4N, v = 16.50m/s

m = 1500 kg

t = 16.5*1500 / 5*10^4

t = 0.495 sec

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