How much work is required to stop an electron

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To determine the work required to stop an electron moving at 1.40×10^6 m/s, the kinetic energy (KE) is calculated using the formula KE = ½mv², resulting in approximately -8.93x10⁻¹⁹ J. The discussion highlights confusion regarding the negative sign, as the work done to stop the electron should indeed be negative, but the question may only require the magnitude of the work. Participants suggest removing the negative sign for the answer, yet the original poster continues to receive an incorrect response. There is a suggestion to verify if the problem specifies the units needed for the answer. Clarifying these points may help resolve the issue.
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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
 
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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.:smile:
 
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.:smile:
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.)
 
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