A truck of mass 2000kg travelling due south collides at an intersection with a car of mass 1200kg travelling due east. The car and truck become entangled and move off to the south-east. The truck driver claims to have been travelling at exactly 60km/hr(the speed limit) just prior to impact. Determine whether the car was exceeding the speed limit.

Question

A truck of mass 2000kg travelling due south collides at an intersection with a car of mass 1200kg travelling due east. The car and truck become entangled and move off to the south-east. The truck driver  claims to have been travelling at exactly 60km/hr(the speed limit) just prior to impact. Determine whether the car was exceeding the speed limit.

drwls · Answer

To have a final southeast direction, the initial momenta of the truck and car must have been equal in magnitude.

If the heavier truck was travelling at the 60 km/h speed limit, the car must have been going 100 km/h.
(100*1200) = (60*2000)