tomwheeler87
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. I am certain that is not right but can't see where i have gone wrong can anyone help me please.

Tom

Last edited:

Homework Helper
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,

whozum
Your solution looks right, its the problem that doesn't make sense. When you get rear ended you don't slow down.

tomwheeler87
Cheers

Cheers people will have words at college tomorrow

Regards
Tom