# Potential and Kinetic Hot Wheels

 Physics: Force, Energy & Motion Relationship Grade Range: Elementary School, Middle School Format: Hands-on

Almost every student will be familiar with Hot Wheels and toy cars, so this is a demonstration that all students can relate to. Be sure to keep track of the cars and where they go!

## Materials

• Hot Wheels Cars or Similar
• Track for Cars

## Safety Precautions

Please read the Physical Demonstrations section of the Demonstration Safety page before performing this demonstration.

## Demonstration

1. Set up the car track. Have the track run along a table, then down a slope before reaching the loop-de-loop. Set out the cars with the track, and set the container at the end of the track to catch the cars.
2. When students come up, ask them what they need to do for the car to drive the length of the track on the table. They will immediately point out that you have to push it, and let them do so. Ask them why the car won't roll down the track without the push. What did the push give the car?
3. Ask the students what they need to do for the car to go through the loop-de-loop. Allow them to try different ways to get the car to do the loop. They will find that the best method isn't to push the car, since they might push it too hard and send it flying. Instead, the best method is to let go of it at the top of the slope! Ask them why they don't need to push the car. What is providing the "push"?

## Why This Works

This little demonstration is a great introduction to the ways Force, Energy and Momentum are all related to each other. When the car is pushed along the level track, the push is a Force on the car, and gives it Kinetic Energy, or the energy of movement. This kinetic energy results in the car having Momentum, meaning that the car is traveling down the track at a certain velocity or speed.

When we have the car travel down the slope to the loop-de-loop, we are watching a Transfer of Energy take place. When the car is sitting at the top of the slope, it has a lot of Potential Energy, or energy to be used. However, while it sits still at the top it cannot use that energy. It needs a push to get going, which it gets from the Force of Gravity that sends the car down the track. Once it reaches the bottom of the slope, right before the loop-de-loop, all the potential energy has been transformed into kinetic energy. This means that the car has a lot of momentum at the bottom of the track, which allows it to go through the loop!