word problem for university level grade 12 physics

Question

On a two lane highway where the posted speed limit is 80 km/h, a car of mass "mc" and an SUV of mass "ms" have a head-on collision. The collision analysts observe that both vehicles come to a stop at the location of the initial impact. Researching the mass of vehicles, analysts found that "ms"=2"mc". Both drivers survived the collision and each claimed to be traveling at the legal speed limit when the collision occurred. It is obvious that the analyst cannot believe both drivers. Use numerical data to explain why.

Answer 1

Allen,

 

      I order for the two cars to come to a dead stop after colliding the momentum of each vehicle had to be exactly equal in magnitude and opposite  in direction since momentum is conserved and it must have been zero initially so it will remain zero after the crash Vs=Vc=0

 

so mc*Vc=-ms*Vs and we know that ms=2mc so mc*Vc=-2mc*Vs so Vc/Vs=2 and the car must have been going twice a s fast as the SUV...

 

Hope this helps

 

Jim

Answer 2

The analyst knows that both are lying. None of them could have survived the tremendous force experienced during the crash, even if one was going at the speed limit. The fact that both survived means that they were both traveling at well below the speed limit.