Question

A boy pushes his baby sister on a swing in the playground. At the top

of the baby's path, she has a potential energy of 200 J.

How much potential energy will she have at the bottom of her path?

How much kinetic energy will she have at the bottom of her path?

Answer 1

* If there is no friction U = 0, K = 200 J

* If there is friction U = 0, K = 200 - W

Step-by-step explanation:

For this exercise we must make an assumption.

* If there is no friction

The energy of the system is conserved therefore the energy is transformed.

The potential energy is

U = m g h

at the bottom of the road there is no height therefore

U = 0

and all the energy has been transformed into kinetic energy

K = 200 J

* If there is friction, which can come from the internal friction of the car, the friction force between the car and the floor, etc.

in this case there is a loss of energy due to the work of non-conservative forces (friction).

The potential energy at the bottom of the path is hedron because there is no height U = 0

The kinetic energy is

K = U -W

K = 200 - W

where W is the work of the friction force.