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Free body diagrams and adding forces

  • Thread starter gbedenba
  • Start date
  • #1
23
0

Homework Statement


In each of the two free-body diagrams, the forces are acting on a 2.6 kg object. For each diagram, find the values of ax and ay, the x- and y-components of the acceleration, with F1 = 5 N and F2 = 3 N. Picture is attached.

(a) Diagram A
ax =____ m/s2
ay =____ m/s2
(b) Diagram B
ax =____ m/s2
ay =____ m/s2

Homework Equations





The Attempt at a Solution



I tried to use sin and cos. I don't think I am adding the forces up right. Help! Due today! I am getting decimal numbers.... I used a = F/M.
 

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Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
7
It is always better to your calculations. We must know what mistakes you have made in adding the forces. That gives un an idea about your level of understanding.
In the first problem, you have to x and y components of 3 N force. Then find net Fx and net Fy which gives you ax and ay.
 
  • #3
23
0
For x comp. of 3N = 1.02606 y= 2.81908

My guess for F net is 2.97394....

ax = F/M 1.14382?


ay = .000354 wrong
 
  • #4
rl.bhat
Homework Helper
4,433
7
Show your ay calculation.
How much significant numbers you are expexted to write in the answer?
 
  • #5
23
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Ax : 3sin(20)=1.02606
F = -1.02606-1+5 = 2.97394 = 2.97394/2.6 = 1.14382

Ay : 3cos(20)= 2.81908
F = -2.81908 + 2.82 = 0.000922 = 0.000922/2.6 = 0.000355
 
  • #6
Doc Al
Mentor
44,940
1,201
Ax : 3sin(20)=1.02606
F = -1.02606-1+5 = 2.97394 = 2.97394/2.6 = 1.14382

Ay : 3cos(20)= 2.81908
F = -2.81908 + 2.82 = 0.000922 = 0.000922/2.6 = 0.000355
Looks good.
 
  • #7
23
0
it says Ay is wrong.

For diagram B...how would I do it?
 
  • #8
Doc Al
Mentor
44,940
1,201
it says Ay is wrong.
Looks right to me. Perhaps they want you to round it off to zero (which is the proper answer, given the significant digits involved).
For diagram B...how would I do it?
The same way you did A.
 

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