Math Is Fun Forum

dharshini

Guest

resultantt of forces

Three forces with magnitudes of 75 pounds, 100 pounds, and 125 pounds act on an object at angles of 30°, 45°, and 120°, respectively, with the positive x axis. Find the direction and magnitude of the resultant of these forces.

Am a math student i dont know physics and my teacher gave methis qn. Can somebody help me with this?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: resultantt of forces

hi dharshini

Welcome to the forum.

The usual method is to resolve each force into a component along the x axis and another along the y axis.

Add up the components.

Then compound them back together.

So for the x components:

Rx = 75cos30 + 100cos45 + 125cos120

For the y components:

Ry = 75sin30 + 100sin45 + 125sin120

Then resultant = square root of Rx squared + Ry squared.

At angle inv tan (Ry/Rx)

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob