#reaction force

I did lots of this in my M1 module but unfortunately have no notes on my blog for it and I threw out all my old college books. I think probably the best things to remember are:

Friction is F = μR so is dependent upon the reaction force R and hence, should be acting at a right angle to R. R is always perpendicular to the surface the body is upon (we'll call it the floor) and is equal to the magnitude of the component of the weight W perpendicular to the floor. This means you'll have to find the component of W which is directly in line with R; R = W sin θ, where θ is the angle the floor is at from the horizontal.

If the body is moving then FR = ma comes into play; where FR is the resultant force on the body, m is the mass of the body and a is the acceleration due to FR. Construct an equation factoring in, for every force, the component along the same line as the motion of the body. Remember force is a vector, so if the force acts in the same direction as the motion it will be positive, if it acts in the opposite direction it will be negative.

When you say motion at angles, I'm not sure if you mean things concerning moments of inertia (in which case, see my posts about moments and torque to get a rough idea), centripetal motion, things traveling along a slope or something completely different.

If you're having difficulty with algebra (since you mention, "using the equations") you may want to have a look at the page I made explaining and making notes on the equations from my physics G481 unit, including some tips on rearranging etc.. For some reason I've never posted a link to it but you may find it useful.