Magnitude and Direction of a charge interaction

AI Thread Summary
The discussion focuses on determining the direction of the force on a -10 nC charge, specifically the angle measured clockwise from the +x-axis. The magnitude of the force is calculated to be 4.3E-3 N. The user initially calculated components of the forces from two other charges but expressed confusion regarding the angle measurement, particularly the clockwise versus counterclockwise distinction. A suggestion was made to clarify the coordinate axes and double-check calculations, emphasizing that the force from the -5 nC charge only has a y-component, while the force from the 15 nC charge has both x and y components. The conversation highlights the importance of accurately interpreting vector directions in electrostatic problems.
themonk
Messages
16
Reaction score
0

Homework Statement


26.P39.jpg

What is the direction of the force \vec{F} on the -10 nC charge in the figure? Give your answer as an angle measured cw from the +x-axis. Problem 26.39 in Physics for Scientists and Engineers Second Edition by Knight
Magnitude of the force is 4.3E-3 N

Homework Equations



As far as I know, this is the only relevant equations:

\vec{F}=k*q_{1}*q_{2}/d^{2}

The Attempt at a Solution


I already found the magnitude as listed above. But I need to find \theta in the clockwise direction.

The force of A (being the -5 nC charge) I figured was direction -4.3E-4 \hat{j} and -1.28E-3 \hat{i} and the other charge had a force of -4.5E-3 I double checked with an answer from someone else (MasteringPhysics also said it was correct). I figured I would use a trigonometric function for the final part, ie the angle measured in the clockwise direction. In lab we used tangent, but was confused as to why (tangent is opposite over adjacent):

tan(\theta)=4.07E-3/1.28E-3 ==> \theta=tan^{-1}(3.179)

which is 72.54 degrees. I added 180 to it to get 252.54, but apparently that is not correct (I don't completely understand the cw and ccw part).

Is there any line of thought that I should proceed with?

(sorry about my English)
 
Last edited:
Physics news on Phys.org
Show the coordinate axes and the forces in your figure, please.

ehild
 
I can't edit the problem, but the x-axis (\hat{i}) is left-right and the y-axis (\hat{j}) would be up-down, if I am not mistaken. The origin would then be at the -10nC.
 
In this case the force on the -10 nC charge from the -5 nC one has only y component, and that form the 15 nC charge has both x and y components. Check your calculation and text.

ehild
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Back
Top