Question

When starting a foot race, a 70.0-kg sprinter exerts an average force of 650 n backward on the ground for 0.800 s. what is his final speed?

Answer 1

Given:
m = 70 kg, mass
F = 650 N, force
t = 0.8 s, time

Calculate the acceleration.
a = F/m = (650 N)/(70 kg)
   = 9.2857 m/s²

Because the initial velocity is zero, the final velocity (after time 0.8 s) is 
v = a*t = (9.2857 m/s²)*(0.8 s)
   = 7.43 m/s

Answer: 7.43 m/s  (nearest hundredth)