Expert Answers
cburr eNotes educator| Certified Educator

Friction is a force that resists the movement of one object along another object.  If they aren’t moving – that is, if the force trying to move them is weaker than the friction -- the friction is static.  If they are moving – so the force trying to move them is stronger than the friction – the friction is kinetic.

If one of the objects is a wheel or ball, you may get rolling friction.  If the force trying to move it is enough to overcome the static friction, the wheel or ball will slide.  However, if it is not enough to overcome the static friction, it will start to roll.  There is still friction during rolling, but it is weaker.

Finally, there is fluid friction.  If one of the substances is a fluid (liquid or gas) there will still be friction. The viscosity of the fluid determines how much friction there is.  So, if you stuff a tube with heavy grease, it will take a lot more force to move it than if it were filled with water.

The cause of friction is electromagnetic attraction between the two objects called molecular adhesion.  To slide the objects you have to break those bonds.  Friction can be increased if the surfaces are very rough or if one is soft enough that one object digs into the softer one.

sid-sarfraz | Student

When we move an object on the floor or any surface, we can feel a force that is pushing the object back or trying to stop it from moving in the direction we are trying it to move, this opposing force is called friction.

Basically friction is the force that resists motion or movement of an object based on the type of surface. The ratio used to measure the frictional force as to the force applied is called the co-efficient of friction.

For example if we try to push the brick on a concrete surface. Here the brick is the object, where as the force applied by us is movement and the force that will try or make it hard for us to push the rock is called friction i.e. the force working in opposite direction. 

ayobose | Student

Friction is the rubbinng between two objects. You see for example the best example of friction is rubbibg your both hands together. It becomes hot. Why? Well your hand is rough everyones is so the two bodies collided together. they kept on rubbing until it became hot. This is friction. Another is striking a lamp against a rough surface

jkakms | Student

The force that one surface exerts on another when two surfaces rub against each other

nado | Student

friction:the force that 2 surfaces exert on each other when they rub against each other

there are 4types of friction

static friction:occureswhen objects aren't moving(ex:abook that u r pushing on the table...)

sliding friction:occures when objects slide past each other(ex:when u go down a slide...)

rolling friction:when objects roll over a surcace area (ex:when u ride a car...)

fluid friction:when a solid object move through FLUIDS:air water...(ex:going down a water slide