# Coaster Energy

A high\-school physics lesson on conservation of energy on a carnival roller coaster at dusk\.

By Numa

Topic: Physics & Chemistry

[Open the interactive Jig](https://ask.jig.com/j/meqK48DccvEu)

## Transcript

### 1. Coaster Energy

This coaster car has no engine\. A motor hauls it up the lift hill once, and gravity does the rest, trading height for speed and back again\. Watch the ride and the energy bars, then grab the car, drag it up the lift and let go\.

Drag the car to move it\. Drag anywhere else to turn the view\.

### 2. 1 · Lifting Stores Energy

Lifting the car takes work, and that work is stored as potential energy: energy from height\. The higher the car, the more it stores\. Drag the car up and down the lift and watch the blue bar follow its height\.

Each clack is a safety catch that stops the car rolling back\.

### 3. 2 · Height Becomes Speed

On the way down, potential energy turns into kinetic energy: energy of motion\. More height means more speed at the bottom\. The car is held at 6 m\. Predict its speed at the speed trap, then drop it and compare\.

Friction is off here\. Try the empty car too: less energy, same speed\.

### 4. 3 · Never Higher Than the Start

With no losses, the car can climb only as high as it started\. The top of the loop is 6 m up, and the car also needs speed to get around the tight curve\. Which drop gets it over, 5 m or 10 m? Choose and watch\.

### 5. 4 · Friction Turns Energy Into Heat

Wheels and air push back on the car, turning some of its energy into heat: the red bar\. The energy isn't gone, so the total stays the same\. But less is left for height and speed, so each climb falls shorter until the car stops\.

### 6. 5 · Brakes Stop the Car

Brakes are friction on purpose\. Pads squeeze a steel fin under the car and turn its kinetic energy into heat in about 1\.5 seconds\. Pull the brake lever beside the track, or use the switch, to close or open the brakes\.

Changing the brakes after the car stops drops it again\. The glow is exaggerated so you can see the heat\.

### 7. Why the First Hill Is the Tallest

A coaster gets its energy once, from a lift or launch, and every later hill is paid for by it\. That's why the first hill is the tallest\. Kingda Ka launched riders to 128 mph, enough to clear its 139 m tower, shown here beside our 10 m lift\.