When you rub your hands together they get warm.
When you push your hands harder together it is more difficult to rub and you have to work harder.
There is more FRICTION.
The WORK you do, also called ENERGY you put in to your hands, makes them warm.
If you turn a dry wooden spindle between your hands, or use a bow with a string to spin it faster, the FRICTION between the tip of the spindle and the wooden base will start to heat up and make the wood smolder!
Add a some dry flammable pieces like thin birch bark and you can start a campfire.
Scouts learn this, and ancient people invented it, they didn’t have matches…
See, no kidding…
The spindle and the hole are black from the heat of the friction, and the birch bark is glowing red hot.
Blow gently and you have the start of a campfire.
When you slide on a smooth floor, say in the gym, you can slide farther than on a sidewalk.
Who would be so dumb to slide on a sidewalk?
What if you run and fall?
the FRICTION on the gym floor and the side walk is different.
Here we go..
Training for football is hard, as you can see…
The friction on the sled, with the weight on it, and dragged over the grass is HIGH, VERY HIGH.
The FORCE of friction is large,
and the player has to pull equally hard to overcome that force…
and move the sled.
Slide on ice and there is almost NO friction, especially if you are on speed skates.
The thin blades have just enough friction between the steel blade and the ice so that the ice melts underneath the blade and the skater slides on a thin layer of water with almost zero friction.
Speed-skating is still hard work because they go so fast they have to push against the air.
Even with zero wind in the stadium they feel wind RESISTANCE or DRAG, because of their speed.
Do you see their tight fitting special suits? The suits are slippery and streamlined to have less drag…
You would never throw sand on the ice, you know why…
Because then there is lots of friction and the speed skaters can’t go.
But if you do that on an icy sidewalk it helps your friends and older people to walk on the ice and not slip and fall.
It’s all about FRICTION.
This Luger slides downhill along a special ice track at speeds of up to 145 kilometer per hour….
See how their clothing is specially made for the least wind friction or lowest DRAG?
When you do skate-boarding, friction is very little with these LOW FRICTION roller bearing wheels!
But when you push off, the friction between your foot and the surface you skate on is HIGH!
The rocking horse head has friction between the wooden body and the steel pole.
That’s because the weight of the head pulls the wooden body down and the body gets stuck by FRICTION between the wood and the steel.
When you touch the head to start it rocking, the friction goes from zero to high friction each time the head bobs up and down.
The wooden body has a hole that is larger than the wire pole and this makes it stick when it does not move!
Yes, but look carefully how bobbing horse moves and you will get it.