Calculating Work and Energy in Electrostatic Systems

AI Thread Summary
The discussion revolves around calculating work and energy in an electrostatic system involving a 1000 kg box on a frictionless ramp. The key points include determining the magnitude of electric charges needed to prevent the box from sliding down the ramp, calculating the box's initial energy, and finding the work required to separate the charges and to push the box up manually. Participants emphasize the importance of balancing the electric force with gravitational force to keep the box stationary. The conversation concludes with one participant expressing that they have resolved their confusion regarding the problem.
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Homework Statement



I decide to use electric charges to move a 1000 kg box up a 30 degree frictionless ramp. I decide to put equal and opposite charges on the box and at the top of the 5.9 meter ramp.

Basically there is a right triangle with a box at the bottom with +q written next to it. The hypotenuse os 5.0 meters and the base angle where the box is standing is 30 degrees. At the top, it says -q

a) what magnitude charges do you need to keep the box from moving?

b) what is the initial energy of the box.

c) How much work does it take to separate the two charges from the 5.0 m apart to infinity?

d) how much work does it take to push the piano up by hand?

Homework Equations



PE=qV

F=kQ1Q2/r^2 (Coulumb's Law)
k = 9*10^9 Nm^2/C^2

The Attempt at a Solution



I think that you have to use cosine/sine somewhere. Also, energy is conserved so that probably has something to do with it.
 
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hockeybro12 said:

Homework Statement



I decide to use electric charges to move a 1000 kg box up a 30 degree frictionless ramp. I decide to put equal and opposite charges on the box and at the top of the 5.9 meter ramp.

Basically there is a right triangle with a box at the bottom with +q written next to it. The hypotenuse os 5.0 meters and the base angle where the box is standing is 30 degrees. At the top, it says -q


Homework Equations



I'm not sure. Maybe Coulumb's law. prob sine and cosine


The Attempt at a Solution



You haven't actually indicated here what problem you are being asked to solve.

Also, you'll have to show some sort of attempt (even a very basic start) at a solution. What have you tried so far on this problem? If you're stuck, what is it that you don't understand?
 
cepheid said:
You haven't actually indicated here what problem you are being asked to solve.

Also, you'll have to show some sort of attempt (even a very basic start) at a solution. What have you tried so far on this problem? If you're stuck, what is it that you don't understand?

I have edited the original thing. Sorry, I forgot about those 2 things.
 
The box is just going to slide down a frictionless ramp due to gravity, in the absence of any other forces. So, in this case, to keep the box from moving, the electric force, which is directed up the ramp, would have to cancel this gravitational force.

You should be able to work out, from the geometry of the situation, what the component of the gravitational force parallel to the ramp is.
 
cepheid said:
The box is just going to slide down a frictionless ramp due to gravity, in the absence of any other forces. So, in this case, to keep the box from moving, the electric force, which is directed up the ramp, would have to cancel this gravitational force.

You should be able to work out, from the geometry of the situation, what the component of the gravitational force parallel to the ramp is.

Hello, but aren't we supposed to use electrostatics and find a magnitude for a charge? I really don't see how gravity will help.
 
Never mind, thanks for your help. I have figured it out.
 
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