What are good things about friction and bad thing about friction

Well, the good things about friction are;
It is responsible for movement because there is friction between the bottom of the shoe and the floor.

It prevents objects from slipping off a material.

It helps in keeping warm. The hands can be rubbed together to produce heat.

It helps in the production of heat when materials are rubbed, therefore creating fires. An example is the match.
 
The bad things about friction;
It causes materials to wear out

It causes materials to tear.

It opposes free movement.

Hope i helped. Have a nice day.

Kinetic energy = 1/2mv^2. since the mass is constant we can form a ratio of it's kinetic energy at 60 divided by that at 30 to see ke(60)/ke(30) = +(60^2)/30^2). this may be said to 300% increase.