Question

. A driver moving at a constant speed of 30m/s sees an accident up a head and hits the brakes. If the car decelerates at a constant rate of -5m/s2, how far does the car go before it comes to stop? A.90m B. 100m C.40m D.20m

Answer 1

Use v^2 = v0^2 + 2aΔx. With v = 0, v0 = 30 m/s, a = -5 m/s^2:

0 = (30)^2 + 2(−5)Δx → 900 − 10Δx = 0 → Δx = 900/10 = 90 m.

Answer: A. 90 m.