What is friction?
Friction is a contact force. It can make an object stay still, or oppose the motion of a moving object.
The problem of friction:
1. Slow down the motion and waste the energy
2. Cause wear
Way to Reduce friction:
1. Air Cushion
2. Use lubricant (WD40 / soapy water / oil (liquid form)/ grease (solid form))
3. Changing sliding motion to rolling motion
4. Stream lized shape
＊ Reduce contact surface area between object can reduce friction.
Making use of friction:
1. Prevent slipping or skidding
2. Hold an object in position
3. Slow down a moving object
4. Move objects
5. Produce heat (kinetic energy --> heat energy + sound energy)