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Original post by Cjm2002
Ive been stuck on this question for a while now can anybody help?
The Question: calculate the momentum of an electron if its kinetic energy is 10keV.
The Question: calculate the momentum of an electron if its kinetic energy is 10keV.
What is the definition of an eV?
Original post by Cjm2002
Ive been stuck on this question for a while now can anybody help?
The Question: calculate the momentum of an electron if its kinetic energy is 10keV.
The Question: calculate the momentum of an electron if its kinetic energy is 10keV.
so kinetic energy = 1/2 mv^2 right?
you already know the mass of an electron as 9.11x10^-31 (Im pretty sure thats what it is anyway).
now you can work out v
and momentum =mv
so just multiply the mass x the speed
hope this helps
Original post by gingeee123
so kinetic energy = 1/2 mv^2 right?
you already know the mass of an electron as 9.11x10^-31 (Im pretty sure thats what it is anyway).
now you can work out v
and momentum =mv
so just multiply the mass x the speed
hope this helps
you already know the mass of an electron as 9.11x10^-31 (Im pretty sure thats what it is anyway).
now you can work out v
and momentum =mv
so just multiply the mass x the speed
hope this helps
btw first convert electron volts to Joules by multiplying by 1.6x10^-19!!
Sorry to bring this back up, I've also been stuck on this question for a bit, here are my workings:
10KeV to J = (x1.6x10^-19x10^3) = (x1.6x10^-16) = 1.6x10^15 J
v=sqrt(2E/m) = sqrt(2(1.6x10^-15 J)/(9.11x10^-31 kg)) = 3.512623491x10^15 m/s (Potentially units wrong)
p=mv = (9.11x10^-31 kg)(3.512623491x10^15 m/s) = 3.2x10^15 kg m/s
Putting this into Isaac Physics D7.7 is incorrect, so is 32 or 3.2 or any similar rounding of the answer.
The most likely thing I'm thinking right now is some error with equations or units, any help appreciated!
10KeV to J = (x1.6x10^-19x10^3) = (x1.6x10^-16) = 1.6x10^15 J
v=sqrt(2E/m) = sqrt(2(1.6x10^-15 J)/(9.11x10^-31 kg)) = 3.512623491x10^15 m/s (Potentially units wrong)
p=mv = (9.11x10^-31 kg)(3.512623491x10^15 m/s) = 3.2x10^15 kg m/s
Putting this into Isaac Physics D7.7 is incorrect, so is 32 or 3.2 or any similar rounding of the answer.
The most likely thing I'm thinking right now is some error with equations or units, any help appreciated!
In detail, you would have (10000 x (1.6 x 10^-19)) = 0.5 x (9.11 x 10^-31) x v^2
- Rearrange to get v = sqrt((2 x 1.6 x 10^-15)/9.11 x 10^-31) = 59.267 x 10^6 m/s
- p = mv, therefore p = 59.267 x 10^6 x 9.11 x10^-31 = 5.4 x 10^-23 kg m/s
- Rearrange to get v = sqrt((2 x 1.6 x 10^-15)/9.11 x 10^-31) = 59.267 x 10^6 m/s
- p = mv, therefore p = 59.267 x 10^6 x 9.11 x10^-31 = 5.4 x 10^-23 kg m/s
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