Answer:
135.7 milliseconds
Step-by-step explanation:
The relationship between force, mass, and acceleration is ...
F = Ma . . . . . we use M for mass, so as not to confuse with m for meters
The relationship between acceleration, velocity, and time is ...
v = at
The fraction of the applied force that is in the horizontal direction is ...
2000N·cos(20°)
Solving for a and t, we get ...
a = F/M
t = v/a = v/(F/M) = Mv/F
t = (85 kg)(3 m/s)/(2000cos(20°) kg·m/s²) ≈ 0.1357 s
The sprinter took about 135.7 ms to push off.
