Question

A car traveling 56 km/h is 22.0 m from a barrier when the driver slams on the brakes. The car hits the barrier 2.15 s later.


(a) Assuming constant acceleration, what was the magnitude of the car's acceleration before impact?
_______ m/s2


(b) How fast was the car traveling at impact?
________ m/s

Answer 1

a. Vo=56km/1h = 56000m/3600s=15.56m/s.

d = Vo*t + 0.5a*t^2 = 22 m.
15.56*2.15 + 0.5a*2.15^2 = 22
33.44 + 2.31a = 22
2.31a = 22-33.44 = -11.44
a = -4.95 m/s^2.

b. V=Vo + at=15.56 - 4.95*2.15=4.92 m/s.