Question

A car with mass 1309 kg is travelling north at a speed of 28.9 m/s. It collides at right angles with a truck (m=2733 kg) travelling east at 16.6 m/s and the two vehicles stick together after the collision. How much kinetic energy is lost during the collision?

Answer 1

The initial velocity of car and truck was

                               

                   and          respectively.

So, the initial momentum of the system was

                 

And the initial kinetic energy of the system was

                   

After the collision, the two vehicles stick together. Let's the final velocity of the vehicle (car + truck) is .

So, the momentum of the system after collision is

                            

From the conservation of momentum, we can write

                            

                      or,  

So, the final speed of the vehicle is

                            

So, the final kinetic energy of the car-truck system is

                            

So, loss in kinetic energy during the collision is