Mini Lab: Does Friction Cause Heat?
Rub a pair of virtual hands for 20 seconds, take an infrared temperature reading, then do it again with graphite on your palms. Record what happens and figure out where the energy goes.
🔥 Hot hands! All that rubbing turned motion into thermal energy.
| Student first name |
Temperature before |
After rubbing hands together |
After rubbing with graphite |
Temperature difference without − with graphite |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Left | Right | Left | Right | Left | Right | Left | Right | ||
| No data yet — finish all three steps above, then add your data. | |||||||||
| Class average | – | – | – | – | – | – | – | – | |
How to use this simulation 7 steps ▼
- Start at Step 1. The hands are at rest, so press Take reading right away. The infrared thermometer shows the starting temperature of the left and right hand — this is your control.
- For Step 2, hold down the red Hold to rub button (or hold the space bar, or drag sideways across the hands). The hands only rub while you are holding, and the 20-second timer only counts down while they are moving.
- The moment the timer hits 0:00, press Take reading as fast as you can. Wait too long and the hands cool off, exactly like they do in the real lab.
- For Step 3, press Apply graphite, then rub for another 20 seconds and take a reading right away. Watch the μ number drop when the graphite goes on.
- Switch the view to Infrared at any time to see the hands as a heat camera does — the color scale on the right tells you what each color means in °C.
- Type your first name and press Add my data to the table. The table fills in your before, without-graphite, and with-graphite temperatures and works out the difference. Everyone in the group can add a row.
- Read the bar chart: taller bars mean a bigger temperature rise. Then finish the energy flow model above. Use Reset trial to run it again, or Cool hands to bring the temperature back to normal without waiting.
The science behind the simulation 4 big ideas ▼
1. Friction happens when surfaces rub
Every surface has tiny bumps and ridges, even ones that feel smooth. When two surfaces slide across each other, those bumps catch and drag. That dragging is friction — a force that pushes back against motion.
Bare skin is rough, so it catches a lot. Graphite is made of flat sheets that slip right past each other, so it catches much less. Scientists put a number on how grippy two surfaces are and call it μ (say "mew"). Bigger μ means more grip.
Friction force = grip number (μ) × how hard you press2. Motion energy becomes heat energy
Your muscles give your hands kinetic energy — the energy that anything moving has. Friction takes some of that kinetic energy and changes it into thermal energy, the energy that makes something warmer.
Heat made each second = grip number × press × rubbing speedSo you get more heat if you rub faster, press harder, or use a grippier surface. The sim shows this number in watts (W) — how much heat is being made every second.
3. Heating up and cooling down at the same time
Thermal energy makes your skin temperature rise. But your hands are also always losing heat to the cooler air around them.
While you rub, you make heat faster than you lose it, so the temperature climbs. The second you stop, you are only losing heat — so the temperature starts dropping right away. That is why you have to measure fast.
4. Energy never disappears
None of the energy is gone. Energy can move from one object to another and change form, but the total amount always stays the same. Scientists call this the law of conservation of energy.
The kinetic energy your hands lose shows up as thermal energy in both hands and in the air. And because each hand pushes on the other, every hand is a source object and a receiver object at the same time.