Gravitational Potential Energy of a Child in a Swing: Ropes Horizontal"

[aaronb]

Homework Statement

A 180 N child is in a swing that is attached to ropes 1.80 m long. Find the gravitational potential energy of the child-Earth system relative to the child's lowest position at the following times.

(a) when the ropes are horizontal

Homework Equations

K_f+U_gf=K_i+Ugi

The Attempt at a Solution

I am confused on how to set up the equation

 

[enricfemi]

it just ask you how to find the potential which can be known by the weight of the child and the length of the ropes.

it doesn't tell you the velocity while the ropes are horizontal, so you can't set up the energy-conservation equation.

 

[nlightner]

for this problem. The gravitational potential energy of a child in a swing can be calculated using the equation U=mgh, where m is the mass of the child, g is the acceleration due to gravity, and h is the height of the child above the ground. However, since the ropes are horizontal, the height of the child above the ground would be zero. Therefore, the gravitational potential energy at this position would also be zero. Additionally, since the child is in motion, the kinetic energy of the child would also need to be taken into account in the equation. However, without knowing the velocity of the child, it is not possible to accurately calculate the kinetic energy. Therefore, the best approach would be to measure the gravitational potential energy at the child's lowest position when the ropes are horizontal and use that as a reference point for calculating the potential energy at other positions.