Magnitude of Impulse

  • Thread starter RevX
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  • #1
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Homework Statement


What is the magnitude of the Impulse exerted on a 920-kg car as it slows from 24.3 m/s to 12.9 m/s while traveling in a straight line?



The Attempt at a Solution


I was thinking 920(24.3 m/s) and 920(12.9 m/s) and subtract the two.

Not totally sure tho.
 

Answers and Replies

  • #2
19
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The Impulse in classical mechanics can be understood as the average force multiplied by the time it is exerted.

J = Faverage (t2 - t1 )

J = ∫ F dt , evaluated from t1 to t2

since F is related to the change in momentum with respect to time,

J = ∫ (dp/dt) dt , evaluated from t1 to t2

here, the dt's cancel, and you get,

J = ∫ dp , evaluated from P1 to P2

so, finally you get to J = p2 - p1 = ΔP

You suggested subtracting the two. Make sure to subtract them in the correct order to obtain the correct sign.
 

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