Question

In an emergency, a driver brings a car to a full stop in 5.0s. The car is traveling at a rate of 38m/s when the breaking begins.

Answer 1

(a) By definition of average acceleration,

a = ∆v / ∆t = (0 - 38 m/s) / (5.0 s)

a = -7.6 m/s²

(b) Recall that

v² - u² = 2 a ∆x

where u and v are initial and final velocities, respectively; a is acceleration; and ∆x is the change in position. So

0² - (38 m/s)² = 2 (-7.6 m/s²) ∆x

∆x = 95 m