Mini Lab: Does Friction Cause Heat?
Rub the hands for 20 seconds and measure how warm they get. Then put graphite on your palms and try again.
🔥 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 with Step 1. The hands are at rest. Press Take reading. The infrared thermometer shows how warm each hand is. This is your control, the reading you compare everything else to.
- For Step 2, press and hold Hold to rub. You can also hold the space bar, or press and hold on the hands. The 20-second timer only counts while the hands are rubbing. When you let go, the hands open to show the palms.
- When the timer reaches 0:00, press Take reading right away. If you wait, the hands cool off, just like real hands do.
- For Step 3, press Apply graphite. The palm side of each hand turns dark gray, fingers and thumb too. The backs of the hands stay the same. Rub for 20 more seconds, then take a reading right away. Watch the μ number. It drops when the graphite goes on.
- Press Infrared to see the hands the way a heat camera does. The color bar shows what each color means in °C. Brighter colors are warmer.
- Type your first name and press Add my data to the table. The table fills in all three readings. It also finds the difference between rubbing without graphite and with graphite.
- Read the bar chart. A taller bar means the hand warmed up more. Then finish the energy flow model. Press Reset trial to try again, or Cool hands to skip the wait.
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.