Question

World-class sprinters can accelerate out of the starting blocks with an acceleration that is nearly horizontal and has magnitude 15m/s^2 .
Part A
How much horizontal force F must a sprinter of mass 64 kg exert on the starting blocks to produce this acceleration?
Express your answer in newtons using two significant figures.

Part B
Which body exerts the force that propels the sprinter, the blocks or the sprinter?
Which body exerts the force that propels the sprinter, the blocks or the sprinter?

Answer 1

Answer:

A. The force exerted by the sprinter must be  9.6 × 10² N.

B. The force that propels the sprinter is exerted by the blocks.

Explanation:

Hi there!

Let´s begin with part B:

The sprinter exerts a force on the blocks and, as a reaction, the blocks exert a force on the sprinter that is of equal magnitude but opposite direction (Newton´s third law). This reaction of the blocks causes the acceleration of the sprinter.

Part A

The force exerted by the blocks can be calculated using Newton´s second law:

F = m · a

Where:

F = exerted force.

m = mass of the object being accelerated.

a = acceleration of the object after applying the force on the object.

F = m · a

F = 64 kg · 15 m/s²

F = 9.6 × 10² N