Ramp and friction: ice, wood, rubber

What the experiment shows

Three identical blocks sit on a 30° slope. Only the friction differs: “ice” (0), “wood” (0.4) and “rubber” (1).

How to run it

1. Press “Run” — the blocks are released at the same time.
2. Notice which block moves first, which moves slowly and which stays.
3. In the editor increase the slope angle and find the angle at which the “rubber” block starts to slide too.

Questions to discuss

• Why is it hard to walk on ice but easy in sneakers with a grippy sole?
• Is friction helpful or harmful? Give examples of both.

The science

Friction holds a body on a slope while the tangent of the angle is smaller than the friction coefficient. At 30°, tan ≈ 0.58: a block with lower friction slides, with higher friction it stays. Smooth surfaces slide, rough ones grip.

Try it at home

Build a ramp from a board and a book. Put an eraser, a coin and an ice cube on it. Raise the board gradually and write down at which tilt each object starts to slide.

What to change in the editor

• Change the blocks’ mass — does sliding depend on mass?
• Shorten the ramp and add a wall at the bottom for a collision experiment.