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Momentum concepts (help please)

  • #1
A car of mass 1348kg moving with a velocity of 26m/s collides with a car os mass 674kg moving with a velocity of 21m/s in the same direction. after they collide the 674kg car moves with a velocity of 5.25m/s


What is the velocity of the 1348kg object?


M1 = 1348kg
M2 = 674kg
V1 = 26ms-1
V2 = 21 ms-1

Ptotalbefore = P1before + P2before
Ptotalbefore = m1before * V1before + m2before * V2before
Ptotalbefore = 1348*26 + 674*21
Ptotalbefore = 49202kgms-1

Ptotalbefore = Ptotalafter
Ptotalbefore = P1after + P2after
49202 – (674*5.25) = P1after
P1after = 45663.6
P1after = m1after * V1after
P1after = V1after
M1after
V1after = 45663.6
...................1348
V1after = 33.88ms-1


According to my answer car1 speeds up from 26m/s to 33.88m/s after the collision. im certain that is not right but cant see where i have gone wrong can any one help me please.

Thanks in advance
Tom
 
Last edited:

Answers and Replies

  • #2
VietDao29
Homework Helper
1,423
1
Uhmmm, the problem itself does not make much sense.
How come the 674 kg car moves with a velocity of 5.25 m / s after the collision??? (5.25 m / s < 21 m / s).
Infact, after the collision, the 674 kg car should have a greater velocity than it had before the collision...
Viet Dao,
 
  • #3
2,209
1
Your solution looks right, its the problem that doesnt make sense. When you get rear ended you don't slow down.
 
  • #4
Cheers

Cheers people will have words at college tomorrow


Regards
Tom
 

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