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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.

Respuesta :

egenriether
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

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