Electric forces and Electric fields question on x and y components

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mattmro
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Homework Statement



please see the pictures!

Homework Equations



F=k(q1)(q2)/r^2



The Attempt at a Solution



okay, I am just curious as to why t cos theta and mg are x components when they are clearly on the y axix!
I thought you used cos for x components and sin for y components
 
Attachments
  • Screenshot of a Cramster solution page showing a free-body style diagram: a string hanging from a ceiling support with tension T, mass m = 8 × 10⁻² kg, charges 0.6 μC and 0.9 μC separated by d = 0.15 m, with Step 1 and Step 2 text below.
    dd.jpg
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  • Screenshot of a cramster.com solution page showing Step 1: a ceiling-hung string with mass m = 8 x 10^-2 kg, a charge of 0.6 µC at the lower left and a charge of 0.9 µC to its right, separated by d = 0.15 m, with tension T along the string.
    ddd.jpg
    35 KB · Views: 512
guys I know I am a DA, i barely got by in physics I and I was able to get by without knowing how to do these type of problems, now I can't please help!
 
The cosine of theta is the adjacent side of the triangle divided by the hypotenuse. With theta defined to be where it is in this problem, T cos theta is the vertical component of the tension.
 
mattmro said:
okay, I am just curious as to why t cos theta and mg are x components when they are clearly on the y axix!
I thought you used cos for x components and sin for y components
Where is it written that they are on X axis ... looks on Y to me
Maybe they took X as Y and Y as X

mikelepore said:
The cosine of theta is the adjacent side of the triangle divided by the hypotenuse. With theta defined to be where it is in this problem, T cos theta is the vertical component of the tension.
OP's asking why the vertical component is called X component
read question again
 
cupid.callin said:
OP's asking why the vertical component is called X component
read question again

I already read the question and the images about ten times before answering. It sounds to me like a teacher may have pounded it into the student's head that x means horizontal and then always take the cos, y means vertical and then always take the sin. I have heard some teachers say that, although it is wrong. The cure for the confusion is to identify the triangle and remember the "sohcahtoa" definitions of sin and cos.