Homework Help: Physics

Posted by arcos15 on Wednesday, September 19, 2012 at 2:43pm.

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

Physics - Henry, Thursday, September 20, 2012 at 8:34pm
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.

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