# Homework Help: Quick question about resolving force

1. Dec 12, 2011

### kougou

[URgent!] quick question about resolving force

1. The problem statement, all variables and given/known data

Hello guys....

I have trouble resolving force into its y- components. Dont laugh. Please have a look on the photo I attached. The force is perpendicular to the slop, and the angle of the slope is given there. And then, what I did is just dot(extend the force), and then use sin(angle) to resolve the force into its component. Of course this is not right, so, why this is wrong. why?

2. Relevant equations

http://img860.imageshack.us/img860/513/xisu.png [Broken]

3. The attempt at a solution

Last edited by a moderator: May 5, 2017
2. Dec 12, 2011

### PhanthomJay

Re: [URgent!] quick question about resolving force

You are incorrectly calculating the force components....the force acts at what angle to the horizontal? (Use geometry). Then find the y component of the force using trig.

3. Dec 12, 2011

### kougou

Re: [URgent!] quick question about resolving force

no, why is this incorrect? where did I mess up?

4. Dec 12, 2011

### kougou

Re: [URgent!] quick question about resolving force

where did i mess up? horizontal is 36 degree, and cos 36 will give x, and sin 36 will give y. but why this is not right?

5. Dec 12, 2011

### Staff: Mentor

Re: [URgent!] quick question about resolving force

The last quote is pretty close to the answer. Now you just have to put an x-y coordinate system on the drawing (like with +x pointing right and +y pointing up), and give the x and y components of that vector in (x,y) coordinates.

Last edited by a moderator: May 5, 2017
6. Dec 12, 2011

### Staff: Mentor

Re: [URgent!] quick question about resolving force

When you resolve a force into its components, none of the components can have a magnitude greater than the force itself.

If you always bear this in mind, then you will correctly sketch the triangle for resolution of forces without confusion.

The components must add together vectorially to equal the force.

They must form a closed triangle of forces: horiz comp + vert comp = force