# Magnitude and direction of the resultant

I am in a high school physics course and NEED some help with this problem.

Four forces act on a hot-sir balloon,

Force upward= 5120N
Force downward= 4050N
Force westward= 1520N
Force eastward= 950N

Find the magnitude and direction of the resultant force on the balloon.

I began to solve it but now I am stuck. This is how I started, did I do this right?

Net Force(Fnet)= EF
EF=5120N+(-4050N)=1070N NORTH

Then,

EF=950N+(-1520N)=-570N EAST OR 570N West

I do not believe that this is the answer that it is asking for. Any help would be greatlly appreciated.

Thank You!
-Lost in Physics

 ebaines Posts: 10,033, Reputation: 5529 Expert #2 Oct 27, 2008, 08:10 AM
You're halfway there. But first, the problem as stated talks about forces upward and downward, but your answer translated that to forces north and south. I'll assume that north, south east, and west are the coordinates you want to work in.

You have correctly determined how to combine the north-south (or up-down) forces into a single vector of 1070 N north and the east - west forces into a vector of 570N west. Now you need to combine these two force vectors into one resultant force vector, which you should be able to see will be in a direction somewhere between north and west. You can do this as follows:

1. Since the west and north forces are perendicular, use the Pythagoran theorem to determine the magnitide of the resultant force.

2. You can determine the direction of the resultant force by using the arctangent of the north force divided by the west force. This wll tell you how many degrees north of west the resultant force vector is pointing.

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