Question

which one is greater dynamic friction or static friction and why?

Answer 1

Dynamic. As it has to overcome static

Answer 2

No thats wrong.. static friction is greater.. thats what we call as the limiting friction.. well tis like this

if there is a box that is kept on a table.. if you don't push.. then there is no friction (i am neglecting the fact that there is air thats pushing it to and indeed there is a lil friction) .. however if you start pushing.. frictions starts pushing in the exact opposite direction with the exact same force which keeps the box stationary... (which is why you find a tough time pushing heavy things.. cause there is a lot of friction).. this is what we call as the static friction.. but we do know eventually we win, thats cause this static friction has a limit.. lets say that limit is 100N.. so until you push with a 100N the box remains stationary.. but the moment you push with lets say 101 N.. the box starts moving now with a net force of 1N.. well thats what you would thing.. but experiments show that even though you are pushing with 101 N .. the box is actually moving with a lil more net force (1.2N if you like).. which tells that somehow that limiting friction has decreased.. and thus we now have a new friction.. friction of motion called the dynamic friction.. which is indeed a lil less than the limiting static friction!

Answer 3

What Mashy says is true. When they are distinguished, static friction is always slightly greater that dynamic friction.