Question

Police are investigating an accident. They know that Tom Brady was driving 20 m/s before being hit by Jay Z head on. Tom Brady’s car has a mass of 1100 kg and Jay Z’s has a mass of 1475 kg. They also know that the two cars stuck together and were traveling 7 m/s in the same direction as Jay Z was driving. The speed limit was 25 m/s, was Jay Z speeding?
Please show work

Answer 1

Answer:

Yes

Explanation:

Momentum before collision = momentum after collision

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

The cars stick together after the collision, so they have the same final velocity.

m₁u₁ + m₂u₂ = m₁v + m₂v

m₁u₁ + m₂u₂ = (m₁ + m₂)v

Plug in values and solve (take Jay Z's direction to be positive):

(1100) (-20) + (1475) u₂ = (1100 + 1475) (7)

u₂ = 27.1 m/s

Yes, Jay Z was speeding.