# Inelastic collision question bus colliding with a car

See below:

If I am not mistaken, P=MV, mass is measured in kg and velocity in m/s...

so, 1km=1000m and 1h=3600seconds,

would it be correct to say, Let car=A and bus =B

Before collision
P=MVa + MVb
P=(900x175/9)+(3500x125/9)
P= 595000/9 km/s

After Collision, their mass combines.
so, 595000/9=4400v
therefore, v=15m/s the speed after combined..
(edited 1 month ago)
Yes, but Id have guessed they want the answer in km/h, so there wouldnt be any need to do the conversion and Id guess km/s should be kg m/s? You can do conservation of momentum for any units (mass, velocity) as long as youre consistent (and know what the answer wants).

Id probably have done it in metric tons so
(70*0.9 + 50*3.5)/4.4
and the result is in km/h, just to keep it simple.
(edited 1 month ago)
Original post by mqb2766
Yes, but Id have guessed they want the answer in km/h, so there wouldnt be any need to do the conversion and Id guess km/s should be kg m/s? You can do conservation of momentum for any units (mass, velocity) as long as youre consistent (and know what the answer wants).
Id probably have done it in metric tons so
(70*0.9 + 50*3.5)/4.4
and the result is in km/h, just to keep it simple.

I see. That's something that wasn't clarified within the unit about which unit it should be expressed in And, yes p=kg/ms.

When doing external research, I found that Newton is traditionally in KG and M/S when referring to mass and velocity, so I wanted to stick with that.

It did note next to the Km/s in the question that it's not the traditional measurement, too.

So, unless specifically asked to express in a unit, best to stick with the unit in the question.
Original post by KingRich
I see. That's something that wasn't clarified within the unit about which unit it should be expressed in And, yes p=kg/ms.
When doing external research, I found that Newton is traditionally in KG and M/S when referring to mass and velocity, so I wanted to stick with that.
It did note next to the Km/s in the question that it's not the traditional measurement, too.
So, unless specifically asked to express in a unit, best to stick with the unit in the question.

SI units (which you did) are usually the way to go especially if you have different terms in the equation. But as this is (roughly)
mv + mv = mv
then the units of m or v dont matter as long as youre consistent.

Usually youd be told what units the answer would be expected in.