Friction is helpful: - We use it to brake for cars - We use it to fly planes -We wouldn't be able to turn a door knob without friction ( Our hand would just slide off it)
Friction harmful: -Our cars would get much better gas mileage without tire and air friction - There would be no skinned knees if friction didn't exist (Like when your skating or football) - We could do some pretty cool dance moves without friction - Our shoes would last longer without friction
