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?

Answer 1

m = mass of tom brady's car = 1100 kg

v = initial velocity of tom brady's car before collision  = - 20 m/s

M = mass of jay Z's car = 1475 kg

V = initial velocity of jay Z's car before collision = ?

V' = velocity of the combination after collision = 7 m/s

Using conservation of momentum

m v + MV = (m + M) V'

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

V = 27.14 m/s