Question

How much work is needed for a 73-kg runner to accelerate from rest to 7.7 m/s?

Answer 1

The work energy theorem states that the work done by all the forces acting on a particle equals to the change in the kinetic energy of the particle.

The expression for the kinetic energy of the body is as follows:

Here, m is the mass of the block and v is the velocity of the body

The expression for the work energy theorem is as follows:

Here, m is the mass of the body, is the final velocity of the body, W is the work done and is the initial velocity of the body.

The expression for the work done by the runner is as follows:

Initially, the runner is at rest. So that, the initial velocity of the runner is as follows:

Substitute for , for , and for in equation and solve for W.

Therefore, the work done by the runner is .