Calculating Kinetic Energy Using the Work-Energy Theorem

In summary, the conversation discusses using the work-energy theorem to determine the kinetic energy of a particle released from rest at a certain distance from a point charge. The approach involves finding the potential at a given distance from the charge, using the equation V = U/qo = 1/4(pi)(epsilon-naught) * q/r, and then using ratios to calculate the potential at the desired distance. The conservation of energy principle is also mentioned as a valid approach.
  • #1
evgeniy
8
0
Hi there,

I am thinking about a problem here,

A particle q produces an electric potential of 6.30E2 V at a distance of 1 m away. If a particle of charge Q=0.00300 C is released from rest at a distance of 8.00 m from q, what will be its kinetic energy after moving very far from q?

My question is, can I use the work-energy theorem here? As in
Ki + Ui = Kf + Uf ?
If I choose a point at 8.00m, then the Ki will be zero, am I right? Then Ui would be Ui = Vi/Q, is this the right equation to use? And then at infinity or very far away, Uf will be zero too. Is this the right approach?

Need help...thanks in advance
 
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  • #2
evgeniy said:
My question is, can I use the work-energy theorem here? As in
Ki + Ui = Kf + Uf ?
That's conservation of energy: sure you can use it.
If I choose a point at 8.00m, then the Ki will be zero, am I right?
Right. It's released from rest at that point.
Then Ui would be Ui = Vi/Q, is this the right equation to use?
No. U = VQ. But how can you find the potential at 8 m? You are only given the potential at 1 m. (Hint: How does potential from a point charge depend on distance?)
And then at infinity or very far away, Uf will be zero too. Is this the right approach?
Yes.
 
  • #3
I see what you are saying.
I kinda get it now. So I am supposed to find a potential at 8m. But...
using the equation V = U/qo = 1/4(pi)(epsilon-naught) * q/r...r is the distance from the point charge q to the point at which the potential is evaluated right? But I do not know the value of a charge of q. So I need to find a charge first since I know the potential at 1m. And after it, I will find the potential at 8m, since now I know the charge. And at the end I will use U = Vq. Am I correct?
 
  • #4
Yes, you are correct. But don't waste any time calculating the charge. Use ratios! (You know that the potential is proportional to 1/r; that's all you need to know.)
 

1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is the energy required to accelerate a given mass from rest to its current velocity.

2. How is kinetic energy calculated?

Kinetic energy is calculated using the formula KE = 1/2 * m * v^2, where m is the mass of the object and v is its velocity.

3. What are the units of kinetic energy?

The units of kinetic energy are Joules (J) in the International System of Units (SI). In some contexts, it may also be measured in foot-pounds (ft-lb) or electronvolts (eV).

4. What factors affect an object's kinetic energy?

The two main factors that affect an object's kinetic energy are its mass and velocity. Objects with larger mass or higher velocity will have more kinetic energy.

5. How is kinetic energy related to potential energy?

Kinetic energy and potential energy are two forms of energy that an object can possess. Kinetic energy is the energy of motion, while potential energy is the energy an object has due to its position or configuration. They are related in that potential energy can be converted into kinetic energy and vice versa, as seen in the law of conservation of energy.

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