Ok I know this is simple but I got 3 points taken off my last exam because it said:

There is a block at rest on an incline, the frictional force acting on the block is...

A)zero B)equal to the weight of the block

C)greater than the weight of the block D)less than the weight of the block

I said (C) greater than the weight of the block because if the friction on the block is greater than the weight wouldn't there not be enough force to make it move? The answer is (D). Why? Did I just get confused about how friction works?

I got it.

Since the box is not slipping we can ignore fs(max)=un.
or fs(max)=umgcos(a)

Thus the fs=mgsin(a)

Weight of box=mg

mg>mgsin(a)

Thanks kpg0001! Too late unknown, maybe next time.

Heh, there were some similar questions earlier on this month itself ;)

Yeah I was mistook the "weight of the block" for the normal force.