Solving Vector Measurement Concerns in Lab

[Agent]

http://img366.imageshack.us/img366/5171/phwq5.jpg Hello there. In lab, we measured vectors. I'm having a little concern on how to get X and Y. If I follow the books method, R_calc comes out too small compare to measure R. (Big % error).

X:
15.5+12.4cos37 = 25.4
Y:
0+9.3sin37 = 5.4
R:
square root of (25.4^2+5.4^2) = 26cmIf I do it my way, R is a lot closer to measure.

X:
15.3+12.4= 27.9cm
Y:
0 + 9.3 = 9.3 cm
R:
square root of (27.9^2+9.3^2) = 29.4 cmThe measurements (x1/2; y1/2; R m) are pretty accurate. What am I doing wrong? Thanks for any help.

 

[hage567]

OK, I will try to point out a couple of things:

http://img366.imageshack.us/img366/5171/phwq5.jpg


Hello there. In lab, we measured vectors. I'm having a little concern on how to get X and Y. If I follow the books method, R_calc comes out too small compare to measure R. (Big % error).

X:
15.5+12.4cos37 = 25.4
I'm not sure I understand what you are attempting, but as I see it your x value is not correct. R is made up of x1 and b in this case. You need to find b, to solve it this way. So use trig to find b instead of x2. But it isn't a right triangle, so the resultant is a little more difficult to solve for.Y:
0+9.3sin37 = 5.4
R:
square root of (25.4^2+5.4^2) = 26cm

This is correct:If I do it my way, R is a lot closer to measure.

X:
15.3+12.4= 27.9cm
Y:
0 + 9.3 = 9.3 cm
R:
square root of (27.9^2+9.3^2) = 29.4 cm


The measurements (x1/2; y1/2; R m) are pretty accurate. What am I doing wrong? Thanks for any help.

 

[m2003]

Hello, thank you for bringing your concerns to my attention. It is important to accurately measure vectors in lab to ensure the validity of your results. After reviewing the data and calculations provided, it appears that there may be some errors in the calculations.

Firstly, it is important to note that in vector addition, the x and y components are added separately and then combined using the Pythagorean theorem to find the magnitude (R). In your first calculation, you have added the x and y components together before taking the square root to find R. This is incorrect and may be why your R_calc is coming out smaller than the measured R.

Additionally, in your second calculation, the x component should be 15.3cos37, not 15.3+12.4. This may also be contributing to the difference in your calculated R.

I would recommend double checking your calculations and ensuring that you are correctly adding the x and y components separately before finding the magnitude. If you are still experiencing significant errors, it may be helpful to consult with your lab instructor or a peer for assistance. Good luck!