Stupid Physics Question

Started by samtheman
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samtheman

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The work done by an external force to move a -8.5 uC charge from point a to point B is 15*10^-4 J.
If the charge was started from rest and had 4.82 *10^-4 J of kinetic energy when it reached point b, what must be the potential difference between a and b?
 
QV = Work = 0.0015 Joules
Q = 0.0000085 Coulombs

One way to look at Voltage:

Voltage is the work done per unit charge.

V = 176.4706 = 180 Volts
 
OK, without thinking too much about it, here's my guess:
V=U/q
U= 15*10^-4 J + 4.82 *10^-4 J
q= 8.5 x 10^-6C

So, V=15x10^-4J + 4.82x10^-4J / 8.5 x 10^-6C
= 233.2 Volts

What do you think?
 
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eikenhein said:
This is not a homework board.
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Yeah, I agree with you. I honestly think that homework threads should be immediately closed for 3 reasons: 1) This isn't a homework board. 2) Some classes actually collect/grade homework and getting a bunch of people on the internet to do homework for you that will be graded is cheating and unethical. 3) The best way to learn material (especially in physics) isn't to have someone give you the answer. It's best for people to encourage you think about problems in different ways without spoon-feeding you the answer.
 
physicsnerd42 said:
Yeah, I agree with you. I honestly think that homework threads should be immediately closed for 3 reasons: 1) This isn't a homework board. 2) Some classes actually collect/grade homework and getting a bunch of people on the internet to do homework for you that will be graded is cheating and unethical. 3) The best way to learn material (especially in physics) isn't to have someone give you the answer. It's best for people to encourage you think about problems in different ways without spoon-feeding you the answer.
Click to expand...

We could do number 3 and help a lot of people in the meantime, including those who've completed all the pre-reqs and are gearing up for the MCAT. I personally don't think there's anything wrong with homework questions as long as people don't give the poster the answer, but just lead them in the right direction by explaining the concept to them. I think it helps everyone. See my thread "dear moderator" for more.
 
Well, do you think my answer is correct? I'm curious what others think.
 
MedStudentWanna said:
We could do number 3 and help a lot of people in the meantime, including those who've completed all the pre-reqs and are gearing up for the MCAT. I personally don't think there's anything wrong with homework questions as long as people don't give the poster the answer, but just lead them in the right direction by explaining the concept to them. I think it helps everyone. See my thread "dear moderator" for more.
Click to expand...

I absolutely agree.
Many homework threads have been closed down, and for good reasons. If everyone were to ask hw questions, this board would become chaotic.
Explaining concepts is fine (go MCAT board) but specific questions should not be allowed.
 
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