Question

A 3000-kg truck moving EAST with a speed of 5 km/hr collides head-on with a 1000-kg car moving WEST with a speed of 10 km/hr. The two vehicles stick together and move with the same velocity after the collision. Determine the post-collision velocity and the direction of the car and the truck?

• A. 1.99 km/hr, EAST
• B. 6.57 km/hr, WEST
• C. 4.25 km/hr, WEST
• D. 1.25 km/hr, EAST

Answer 1

The correct option is D

1.25 km/hr, EAST

Momentum of Truck: 3000 $\times$ (+5) = + 15 000

Momentum of car: 1000 $\times$ (-10) = -10 000

Total = Truck + Car

= + 15 000 + (-10 000)

= 5000

After collision:

Momentum of Truck: 3000 $\times$ v

Momentum of car: 1000 $\times$ v

We know that the total momentum of system remains conserved

5000 = 3000 $\times$ v + 1000 $\times$ v

5000 = 4000 $\times$ v

V = 1.25 km/hr , will move towards east.