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. You work your hands to overcome FRICTION and the WORK or ENERGY you put in 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 dry and 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, just 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, (of course, who would slide on a sidewalk unless you fall and hurt yourself…) the FRICTION on these surfaces is different.
Here we go, training for football is hard, the friction of the sled, with the weight on it and ragged over the grass is HIGH, and the fellow in training is pulling hard.
The FORCE of friction is large, and the player has to pull equally hard to overcome the force of friction 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 and he wind speed acts against them.
Throw sand on the ice and there is lots of friction. You would never do that, but if you do that on an icy sidewalk it helps prevent people slipping and falling.
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 skate-board, friction is very little with these low friction roller bearing wheels!
When you push off, the friction between your foot and the surface you skate on is high!
The rocking horse head or Pole Robot has friction between the wooden body and the steel pole; because the weight of the head pulls the wooden body down the body gets stuck by FRICTION between the wood and the steel. When you touch the head to start it bobbing on the spring that connects it to the body, the friction goes from zero to full friction at each up and down bob and this becomes a self re-enforcing motion down the pole. The wooden body has a hole that is larger than the wire pole and this makes it stick when it does not move!
Difficult? Yes, but look carefully how Pole Robot moves and you will get it.
Science and Technology takes patience and some experimentation but it is fun!