BIO? World-class sprinters can accelerate out of the starting blocks with an acceleration that is nearly horizontal and has magnitude 15 m/s2. How much horizontal force must a 55-kg sprinter exert on the starting blocks to produce this acceleration? Which body exerts the force that propels the sprinter: the blocks or the sprinter herself?

Solution 21E According to newton’s second law of motion,the net force acting on an object of mass m,produces an acceleration a. Newton’s second law F = ma. Here m is the mass and a is acceleration. Given data: Mass of sprinters m = 55 kg. Sprinter's acceleration a = 15 m/s . F = ma F = (55 kg)(15m/s )2 F = 825 N This is the force applied to the sprinter by the blocks.