Forces & Friction question!

1. Dec 7, 2012

aoo

A 5 kg block rests on a 30degree incline
the coefficient of static friction is between the block and incline is 0.2
how large a horizontal force must push on the block if the block is to be on the verge of sliding a)up the incline and b) down the incline

So far I have ma=Fapp-(m)mg-mgsin30
where (m) is miu or friction co-efficient

ive been working on this for a long time but not sure how to get the answers
any help will be much appreciated!

2. Dec 7, 2012

Simon Bridge

Welcome to PF;
Would you be able to do this if the block were not on an incline?

So far you have $ma=F_{app}-\mu_kmg - mg\sin{\theta}$ (resist the urge to put the numbers in so soon).

Is this for pushing the block up or down the slope?
Which direction does friction act?

According to the description: what is the acceleration?