# Q & A: The force in bungee jumping.

Q:
what force is used when coming back up in bungee jumping?
- Callum (age 12)
england
A:
Hello Callum,

The force used in coming back up in bungee jumping is due to the contraction of the elastic fibers in the bungee cord. Here's a simple explanation of the mechanics involved in a bungee jump.

When a person does a bungee jump, he would usually jump from a high place--which means he starts off with a large gravitational potential energy.

As he plummets downwards, the potential energy in his body is being converted to kinetic energy--allowing him to increase his downwards velocity.

Once the bungee cord (attached to the person's body) extends pass its rest length, it will start exerting an upward force on the person's body--slowing him down. This upward force increases as the bungee cord gets more stretched. In addition, the extension of the bungee cord allows potential energy to be stored in it.

Finally, the person's body comes to a stop, the kinetic energy in his body has converted to potential energy in the bungee cord. At this point, the fibers in the bungee cord are stretched and have stored a large amount of potential energy. The fibers then contract, and pull the person's body upwards.

The upwards force will then pull the person's body upwards to a certain height--which would be lower than what he began with due to loss of energy. Then, the person would fall again, repeating the process of falling and rising--which is the most exciting apart of bungee jumping!

Maurice
P.S. I have attached a diagram below to help you visualize the mechanics involved in bungee jumping.

(published on 03/05/2012)