The Gripping Force
Friction — the force that rubs both ways
What this lesson covers
Why it matters
Without friction you couldn't walk, write, or even hold this tablet — everything would slither away. With too much of it, machines groan and shoes wear out. Meet the force that rubs both ways.
Predict first
A rolling ball on grass stops sooner than on smooth ice because…
Friction is the gripping force between rubbing surfaces — rough grips harder, smooth lets things slide. It comes in three types: STATIC (holding still things still), SLIDING (dragging), and gentle ROLLING (wheels).
- grass gives more friction — correct
- grass is greener
- ice pushes the ball forward
What you do
Give the ball the SAME push on ice, floor, carpet and sand — then put it on rollers and feel friction change its type.
Check yourself
We can WALK because friction…
On frictionless ice your shoes have nothing to grip — every step slips.
To REDUCE friction in a bicycle's wheels we…
Oil smooths the rub; sand ADDS grip (that's why it's thrown on icy roads).
Shoe soles have patterns (treads) to…
More grip where you want it — friction is a tool, dialled up or down by design.
- grips our shoes against the ground — correct
- pushes us from behind
- doesn't exist on footpaths
- oil the bearings — correct
- add sand
- ride slower
- INCREASE friction and stop slipping — correct
- look sporty
- make shoes lighter