An Olympic track runner starts from rest and has an acceleration of 1.9 m/s2 for 3.7 s, then has zero acceleration for the remainder of the race. Find the runner's speed (in m/s) at the following times.

a) t = 0    v = 0, b) t=3.7 s v = 7.03 m / s , c) t>3.7 s  v = 7.03 m / s

Explanation:

They ask us to find the speed of the runner for various times

a) when the race starts

         t = 0    v = 0

part of rest

b) for t = 3.7 s when acceleration ends

        v = v₀ + a t

        v = 0 + 1.9 3.7

        v = 7.03 m / s

c) for t> 3.7 s

     In this case the acceleration is zero a = 0

So its speed is constant

            v = 7.03 m / s

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.