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A car is at rest when it experiences a forward propulsion force to set it in motion. It...

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happyface22 | Student, Grade 11 | (Level 2) Honors

Posted January 3, 2012 at 9:46 AM via web

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A car is at rest when it experiences a forward propulsion force to set it in motion. It then experiences a 2nd forward propulsion force to. . .

speed it up even more. Finally, it brakes to a stop. Find the Impulse, Change in momentum, and the momentum for each car. The Total application of force is 4000 N and the time it takes is 4.0 seconds. Please explain how to solve and thanks for your help :) Have a blessed day!

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ndnordic | High School Teacher | (Level 2) Associate Educator

Posted January 3, 2012 at 10:12 PM (Answer #1)

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This question uses a form of Newton's Second Law:  F=ma, recognizing that a = delta v/deta t.

Rewrite the equation:

F = m *delta v/delta t.

Now rearrange:

F*delta t = m * delta v

F* delta t = the impulse

m * delta t = the change in momentum.

In essence it says a given impulse will produce a given change in momentum.

In your example, F = 4000 N & delta t = 4.0 seconds.

So the impulse is 4000 N * 4.0 s = 16,000 Newton seconds

therefore, the change in momentum is also 16000 Newton seconds

You can use this relationship to force, contact time, mass of the object, or the change in velocity produced - given the other three variables.

Sources:

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