Need help finding change in velocity and momentum

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Homework Help Overview

The problem involves an automobile collision where one vehicle crashes into a parked vehicle, and the discussion centers on calculating the change in momentum and velocity due to friction over a specified time interval.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the calculations related to momentum and frictional forces, with some questioning the accuracy of the input values used in the computations. There is also a focus on the implications of the mass of the vehicles involved.

Discussion Status

Some participants have verified calculations and expressed agreement on the results, while others are exploring potential errors in the input values. The conversation reflects a collaborative effort to clarify misunderstandings regarding the problem setup.

Contextual Notes

Participants note discrepancies in the mass used for calculations, which may affect the results. The discussion includes the conditions of the vehicles involved, such as whether the offending vehicle had its brakes applied.

Sneakatone
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An automobile of mass 1500 kg traveling at 24 m/s crashes into a similar parked automobile. The two automobiles remain joined together after the collision. Suppose that the collision last for 0.020s, and pavement with a coefficient of friction uk=0.63. What change of momentum and what change of speed does the friction force produce in the joined automobiles in the interval of 0.020 s ?

Delta p=?
Delta v=?

for p I did 24m/s *1500kg=36000
3600/12m/s=3000
The Friction force = µ . m . g =0.63*9.81*3000=18541 N
The change in momentum produced by this force = F . t =18541*0.02=371 kg*m/s
delta p=36000-371=35629 kg*m/s

to get v
35629/3000=11.87m/s
12m/s-11.87m/s=0.15 m/s
 
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What exactly do you need help with?
 
the numbers that I input are apparently wrong.
 
I am not sure what you mean by this. I have checked your computations and my results agree with yours.
 
Sneakatone said:
The Friction force = µ . m . g =0.63*9.81*3000=18541 N
Does the offending vehicle have its brakes on?
 
it does not
 
Sneakatone said:
it does not

So... what's the error in the equation I quoted?
 
I should have used 1500kg for mass instead.
 
Sneakatone said:
I should have used 1500kg for mass instead.
Exactly. Does it accept your answer now?
 

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