• Support PF! Buy your school textbooks, materials and every day products via PF Here!

A vector problem

  • Thread starter cowgiljl
  • Start date
63
1
It wants me to find the magnitude and direction of the resultant
F1 = 75.0 Newtons, 25 degrees east of north
F2 = 100 Newtons 25 degrees east of south

i drew a picture again
I took the for F1 sin 25 * 75 and got 31.69
F2 cos 25 * 75 and got 67.97

Sin 25 * 100 = 42.67
cos 25 * 100 = 90.63

So then i added the 31.69+(-42.67) = -10.98
and added 67.97+90.63 = 158.60

used the C^2 = A^2 + b^2 C^2 =158.60^2+10.98^2
C = 158.98 N
Tan -1 (158.60/-10.98)
and theata was = to a -86.04 degrees east of south

is that one right??????
 

jamesrc

Science Advisor
Gold Member
476
1
I think you should double-check how you added the components. The x-component of the force (if we label east as x and north as y) should by (F1+F2)sin(25) and the y-component of the force should be (F1-F2)*cos(25). From your diagram, you should ree that the resultant vector points roughly ESE
 

NateTG

Science Advisor
Homework Helper
2,449
5
Originally posted by cowgiljl
It wants me to find the magnitude and direction of the resultant
F1 = 75.0 Newtons, 25 degrees east of north
F2 = 100 Newtons 25 degrees east of south

i drew a picture again
One of the ways to add verctors is to draw them head to tail with each other. You might not get an exact answer, but it often makes it easy to check your answer.

I suspect that you aren't keeping track of which component is which well enough.

You might do better if you drew them in and labled them x1 y1 and x2 y2 for F1 and F2 respectively. It would also make it easier for others to follow your work.

From looking at the excercise, I would guess that the resultant force should have a magnitude of about 50N and be pointing roughly southeast
 

HallsofIvy

Science Advisor
Homework Helper
41,712
876
So then i added the 31.69+(-42.67) = -10.98
and added 67.97+90.63 = 158.60
You might find that it helps YOU (not to mention us) if you labeled these better. The 31.69 and 42.67 you got using sin(25): is that "east-west" or "north-south". Once you are sure of that, think about which ways the forces are in the "same direction" and which opposite.
 

Related Threads for: A vector problem

Replies
9
Views
2K
  • Posted
Replies
3
Views
848
  • Posted
Replies
1
Views
1K
Replies
1
Views
6K
  • Posted
Replies
5
Views
2K
  • Posted
Replies
4
Views
4K
  • Posted
Replies
1
Views
898
  • Posted
Replies
2
Views
650

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top