Vector Physics Help: Find Resultant Force & Equivalent Force

[pirateyoshi]

Three forces acting upon axis, need to find resultant force and the (equivalent?) force as well.



2. Frx=84 Grams -> Fry=116 grams up.



3. I had already found the Resulant X and Y from the three orginal forces (200g @ 20 degrees, 100g at 100 degrees and 100g at 210 degrees) but i am having diffuculty with trying to figure out the direction of the resultant force (I believe the magnittude is ~143g) Its my first assignment in physics and I am already lost :[

 

[rootX]

use trigonometry.
tan t = y/x

edit: you didn't round Fry correctly, it's like .88
so it should be 117?

P.S. A nicer way to solve vectors, if they are given like that:
in calculator (that also shows input on the screen-CASIO fx991)
200*cos20+100*cos100+...
store the result in memory,
and then just change 'cos' to 'sin'

and now divide this by stored number, and inverse trig would give the theta

 

[pirateyoshi]

I really should blame my geometry teacher but... maybe I should have picked it up myself. Now, y/x gives me ~1.38. Now is there an equation or a function on a calculator that inverses the decimal into a degree? (Sorry if that's what you already mentioned.)

Possibly something about an inverse tangent?

 

[rootX]

no i didn't mention it.

it should be above "tan"

 

[pirateyoshi]

P.S. A nicer way to solve vectors, if they are given like that:
in calculator (that also shows input on the screen-CASIO fx991)
200*cos20+100*cos100+...
store the result in memory,
and then just change 'cos' to 'sin'

I get what you are saying there, thanks for the tip. 117/84 = ~1.39. Now I understand that to be the tangent. I know that all angles have a number to match (such as Sin at 30 degrees is .5) but what I don't know is how to get to .5 to Sin 30 for example.

 

[rootX]

when 0.5 is there on the screen
press "shift"
and then sin button

 

[pirateyoshi]

...I am almost too embarrased to say that I was using the Windows calculator. Thanks a lot for the help. I am just in 10th grade so all these classes I am getting together are getting me flustered. Ill go borrow my friends and continue.

 

[rootX]

for windows, go to view>scientific

and then select "Inv" option (it's below "Hex" - on the left side of the calculator)
and then click "sin"

 

[pirateyoshi]

Ok I strictly remember doing that and it gave me a smaller decmial. This result (54.2 degrees) is far more logical. Thanks rootX. Used Sin of 54 degrees to confirm that hyp = ~144g and now I know that its at 54 degrees.Adding 180 degrees to hat gives me the Fe of 144g at 234 degrees. ^^ Thanks for the help!