# How much work is required to stop an electron

• rperez1
In summary, the question asks for the amount of work required to stop an electron with a given mass and velocity. The correct answer should be the magnitude of the work, without the minus sign, but it seems that the answer is still being marked as incorrect. It is possible that the units specified in the question are different from the units used in the calculation.
rperez1

## Homework Statement

How much work is required to stop an electron (m=9.11×10−31kg) which is moving with a speed of 1.40×10^6 m/s ?

2. Homework Equations

## The Attempt at a Solution

E.g a particle has KE=10J. The work that must be done on it to stop it is -10J.

So work out the kinetic energy of the electron(½mv²) and put a minus sign in front. I get -8.93x10⁻¹⁹ J.but when i answer the question it says i am wrong? can someone please help me

No need of minus sign dear.
Minus sign represents the direction. But question don's ask a direction. So remove the minus sign. Then it'll be okay.

rperez1 said:
E.g a particle has KE=10J. The work that must be done on it to stop it is -10J.
Technically, you are correct: The work done must be negative. But apparently they just want the magnitude of the work, not the sign.

Doc Al said:
Technically, you are correct: The work done must be negative. But apparently they just want the magnitude of the work, not the sign.
it still says incorrect when i take out the negative which makes no sense bc i have no other way to get another answer.

Jimmy Moriaty said:
No need of minus sign dear.
Minus sign represents the direction. But question don's ask a direction. So remove the minus sign. Then it'll be okay.
it still continues to say that it is incorrect, which makes no sense bc i know i did it correctly, i have no other way to get another answer. i don't know what is wrong with my answer.

Do they specify the units they want you to use? (Joules makes sense, but there are other units.)

## 1. How is work defined in terms of stopping an electron?

Work is defined as the force applied to an object multiplied by the distance the object moves in the direction of the force. In the case of stopping an electron, work is the force required to bring the electron to a complete stop.

## 2. What factors affect the amount of work required to stop an electron?

The amount of work required to stop an electron depends on the initial velocity of the electron, the strength of the force applied, and the distance over which the force is applied.

## 3. Is it possible to completely stop an electron?

Yes, it is possible to completely stop an electron. However, this would require an infinitely strong force acting over an infinitely small distance, which is not physically possible.

## 4. How does the work required to stop an electron compare to the work required to accelerate it?

The work required to stop an electron is equal to the work required to accelerate it to its initial velocity in the opposite direction. This is based on the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred from one form to another.

## 5. Can the work required to stop an electron be calculated?

Yes, the work required to stop an electron can be calculated using the formula W = Fd, where W is work, F is force, and d is distance. However, this calculation may be complex as it requires knowledge of the initial velocity and the strength and direction of the force acting on the electron.

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