A couple quick questions on friction?

Question

What is the effect of friction on a moving object?

How is an object able to maintain a constant speed when friction acts upon it?

Thanks for you help!

Answer 1

in simplest terms, friction applies a force on an object that opposes the motion of the object

let's think now of a crate sliding across a floor; there is a force of friction acting in the direction opposing the motion of the crate.  Now, what we know about physics is that forces cause CHANGES in motion...if there are no NET forces, then there are no changes in motion.  

An object can move at constant speed when there is friction if and only if there is a force pushing the object in the direction of motion and the magnitude of this force exactly equals the amount of friction.  In this case, the net force acting on the object is zero, and the object experiences no change in motion.  In other words, the object moves at constant velocity across the floor.

hope this helps