i need SERIOUS PHYSICS help- I BEG OF THEE SMART PEOPLE?

Question

OK. SO, Ff= (mu)Fn (also known as the FUN equation-as likely as not!) anyways, i know the Fn, and i need to find the frictional force. Then there is this EVIL coefficient of friction. and this is where i crumble. so i have the coefficient of static friction and the coefficient of kinetic friction (this is all about a block of wood sliding across a table by the way) and now i need to know the frictional force. BUT to find the frictional force, i need the coefficient of Friction. HOw do i find this?? do i use the kinetic coefficient? What does this mean?? PLEASE HELP ME. thank you very much

Answer 1

This is bone simple kid. Ff=(mu)Fn SO mu = Ff/Fn

Mu, aka the EVIL coefficient of friction, is just the ratio between Ff (the force opposing motion) and Fn (the Force pressing the two surfaces together)

Mu comes in two flavors, static & kinetic.

Typically the force required to get something to move, is higher than the force required to keep it moving. So for your block of wood on a table, if you multiply its Fn by the static coefficient of friction (mu static) you get the force required to start the block in motion; & if you multiply Fn by the kinetic coefficient of friction (mu kinetic) you get the force required to keep the block in motion.

Hope that helps.

Answer 2

You need the mass of the object...

Then multiply the mass of the object by 9.8, this would be FN

Then plug it into the equation using the kinetic coefficent, as it appears that the object is in motion, that should get you Ff