1The two things in the tug-of-war
Grip holds you. Tilt pulls you down.
Whenever something might slide, two forces fight. Watch each one on its own:
Grip (the stickiness)
How hard two surfaces hold each other. Rough, rubbery stuff grips tight. Glassy, icy stuff barely grips at all. It's about the pair that's touching.
Tilt (the downhill pull)
Gravity always tugs straight down. But the steeper the slope, the more of that tug points down the ramp — trying to start a slide.
2Same block, two floors
A gritty ramp vs a glassy ramp
The grippy floor
Think rubber soles on a rough sidewalk. The two surfaces grab each other hard, so grip wins the tug-of-war easily. The block just sits there.
The slippery floor
Now picture the same block on ice. The surfaces barely grab at all, so there's almost no grip to fight the downhill pull. The tiniest tilt and… off it goes.
3Your turn — build a ramp
Drive the tug-of-war yourself
Change the grip of the floor and the tilt of the ramp. Watch the two arrows fight: the amber downhill pull vs the most the teal grip can hold. When the pull beats the grip, the block lets go.
4The trick question
Two ramps, the EXACT same tilt 🧊
Here's the catch: both ramps are locked at the very same gentle angle. One is icy, one is rubbery, with the same block on each. If only steepness mattered, they'd do the same thing… right?
Guess before you find out
Same block. Same gentle tilt. One ramp is icy, one is rubbery. What happens?