A dart with a mass of 0.5kg is thrown at 15m/s and sticks into a 1kg apple hanging on a string. What is the total momentum of the objects before the collision?

Before the collision:

m v1 = .5 kg * 15 m/s = 7.5 kg-m/s

Incidentally, after the collision

(M + m) v2 = 7.5

v2 = 7.5 / (1 + .5) = 5 m/s

with 5 seconds, no, but over time if the police car stays at 65m/s ad the speeding car stays at 60, then obviously yes, but the answer to your question would be, no.

hope this : )