Speed, Kinetic Energy, and Power in a sprinter...?

Question

A sprinter who weighs 670 N runs the first 7.0 m of a race in 1.6 s, starting from rest and accelerating uniformly. What are the sprinter’s (a) speed and (b) kinetic energy at the end of the 1.6 s? (c) What average power does the sprinter generate during the 1.6 s interval?

Answer 1

Distance d = 0.5*a*t^2 so a = 2*d/t^2 = 14/2.56 = 5.469 m/s^2.
v=a*t = 5.469*1.6 = 8.75 m/s.
his mass = 670/g = 68.321 kg
Kinetic energy ke = 0.5*m*v^2 = 2771.6 j
Ave. power p = ke/t = 1732.2 w
Note: I used 9.80665 m/s^2 as grav. accel g.