View Full Version : Net Forces
 
 HSPhysics1001
Oct 11, 2013, 04:04 PM
What is the net force (or single equivalent force) of the following three forces
 
F1- 50N East, F2-30 N NE and F3 60N W40degreesN. 
(Answer as a size and direction)
 ebaines
Oct 14, 2013, 07:12 AM
When adding forces you start by breaking each force into orthogonal consituent parts - i.e a force component acting north + force component acting east.  Then you add all the north comnponents of the three forces to get a total north componenet, and do the same for the east components of all three forces.  Finally combine these totals into a single force with magnitude and direction.  Post back with your attempt and we'll be happy to check it for you.
 HSPhysics1001
Oct 14, 2013, 10:57 AM
How do I deal with F2 and F3? Im not sure what to do because one is going NE and  the other is going a 40 degree angle. 
 
My attempt: 
 
F1-50N East
 
F2- 
I decided to solve by finding the x and y components and because its at going NE used 45 degrees as the angle. 
 
Y-comp. 30Sin(45)=21.2N
X-comp. 30Cos(45)=21.2N
 
F3-
Y-comp 60Sin(40)=38.6
X-comp 60Cos(40=46N-Which is negative because its going West
 
Anding them together
X-Comp- 50N+21.2N+-46N=25.2N to the East
Y-Comp-21.2N+38.6N=59.8N North
 ebaines
Oct 14, 2013, 11:04 AM
Looking good so far.  Last step is to combine the horizontal and vertical components of force.  The magnitude of the resutant force vector comes from Pythagorus:
 
 |F| = \sqrt{F_x^2 + F_y^2} 
 
and the angle can be found from
 
 \theta = Arctan(Fy/Fx)
 
Be careful when doing the arctangent calculation to be sure which quadrant  \theta should be in.
 HSPhysics1001
Oct 14, 2013, 03:44 PM
Awesome thanks! 
 
64.8N and 67.1
 ebaines
Oct 15, 2013, 05:24 AM
Awesome thanks! 
 
64.8N and 67.1
 
Be careful to define how the angle you got of 67.1 degrees is measured.  Is it a bearing from north?  Or degrees north of east?