A 47.9-kg skater is standing at rest in front of a wall. By pushing against the

The average force that the skater exerts on the wall has a value of 107.77 Newtons with opposite direction to that of the wall (with positive sign).

Explanation:

The average force can be found employing Newton's second law:

(1)

Where F is the force, m is the mass and a is the acceleration.

The acceleration can be determined employing the equations for a Uniformly Accelerated Rectilinear Motion:

(2)

Replacing equation (2) in equation (1) it is gotten:

(3)

Since, the skater was standing at rest before pushing against the wall, her initial velocity will be zero ()

But , therefore:

This result represents the force that the wall applies to her (as the sign shows)

According with Newton's third law, the average force that the skater exerts on the wall has a value of 107.77 Newtons with opposite direction to that of the wall (with positive sign).

Notice, that the backward direction is considered as the negative direction.

When the apple falls from the tree, it has some gravitational potential energy due to its height. Now, When it starts falling, the Gravitation Potential energy will starts converting into the Kinetic Energy. When the apple is about to strikes the ground, the Gravitational Potential energy have been converted into the Kinetic Energy.

Explanation: