# Homework Help: Three forces acting on a point

1. Oct 12, 2008

### Phantom5800

I'm sorry that this is probably a repeat topic, but I am having a hard time using other threads as examples. This is probably really easy, I just can't seem to figure it out the way our teacher taught it. I'll try and make this short and simple.

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

There are three forces acting on a single point. One is 15 N north; the second is 15 N west; and the final is 15 N at 30 degrees east of north. Determine the magnitude and direction of the resultant force.

2. Relevant equations

Basic trig (sin, cos, tan), a^2 + b^2 = c^2. This is all we have been taught in this class and are expected (and should be able to) solve with just this.

3. The attempt at a solution

PHP:
10 N north
|  /
| /   15 N 30 degrees east of north
<-----------|/
15 N west
From there I am unsure of what I could do to easily solve it (also a little unsure of what I am even solving for).

Last edited: Oct 12, 2008
2. Oct 12, 2008

### Staff: Mentor

One easy way to add vectors is to find their components (x & y = East-West & North-South) and add them. Then you can find the magnitude and direction of the resultant from its components.

3. Mar 9, 2011

4. Mar 9, 2011

### Staff: Mentor

If an object is in equilibrium, the forces acting on it (which are vectors) must add to zero. Is that what you mean?

5. Mar 9, 2011

### 24hourtutor

For the original poster: any question like this, even one with 2034 forces acting on a point, can easily be solved by breaking each vector into x and y components and then adding up to find the resultant. Some people find a chart helpful.

V| x | y
1| 0 | 10
2|-15| 0
3| ?x| ?y

The total in the x direction would be -15 + ?, and the total in the y would be 10 + ?y.

To find ?x and ?y will require some trig.

6. Mar 9, 2011