Question

A 2000 kg minivan runs into a 800 kg car that was at rest at a stop sign and they stick together. If the compact car does not stick to the van but, instead, causes the minivan to come to a complete stop. How fast will the car be going after the collision?

Answer 1

Answer:

 v₂ = 2.5 v₁

car leaves at 2.5 times the speed of the minivan

Explanation:

This is an exercise of conservation of the momentum, to solve it we create a system formed by the minivan and the car, therefore during the crash the forces are internal and the momentum is conserved.

Initial instant. Before the crash

        p₀ = M v₁+ 0

Final moment. After the crash

        $p_{f}$ = M 0 + m v₂

how momentum is conserved

         p₀ = p_{f}

         M v₁ = m v₂

         v₂ = $\frac{M}{m}$ v₁

           

let's calculate

        v₂ = 2000/800 v₁

        v₂ = 2.5 v₁

therefore the car leaves at 2.5 times the speed of the minivan