At the start of his race, an 81-kg runner pushes against the starting block, exerting an average force of 1600 N . The force that the block exerts on his foot points 20∘ above the horizontal. Determine the horizontal speed of the runner after the force is exerted for 0.28 s.
The force in the horizontal direction is given by 1600cos(20)=1503.5N Given the mass of m=81kg, we can use F=ma to get acceleration F/m=a a=1503.5/81=18.56m/s² The velocity is given by the integral of the acceleration, V=18.56t m/s since t=0.28s we get v=18.56(0.28)=5.197m/s
