1.

A car of mass 400 kg and travelling at 72 km-h^(-1) crashes into a truck of mass 4000 kg and travelling at 9 km-h^(-1), in the same direction. The car bounces back at a speed of 18 km-h^(-1). The speed of the truck after the impact is

Answer»

`9 km-h^(-1)`
`18 km-h^(-1)`
`27 km-h^(-1)`
`36 km-h^(-1)`

SOLUTION :`m_(1) = 400 kg, u_(1) = 72 kmh^(-1) = 72 X 5/18= 20 ms^(-1)`
`m_(2) = 4000 kg, u_(2) = 9 kmh^(-1) = 9 x 5/18= 2.5 ms^(-1)`
`V_(1) = 18 kmh^(-1) = 18xx5/18= 5 ms^(-1)`
From Law of Conservation of momentum
`m_(1)u_(1)=m_(2)u_(2)= m_(1)V_(1)=m_(2)V_(2)`
`IMPLIES 400xx20+4000xx2.5=400xx(-5)+4000xxV_(2)`
`v_(2)=20,000/4000`
`v_(2) = 5 ms^(-1)= 5xx18/5-= 18 kmh^(-1)`


Discussion

No Comment Found

Related InterviewSolutions