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# Physics Unit 4 Multiple choice question

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1. Two electrons x and y travel at right angles to a uniform magnetic field. X experiences a magnetic force, Fx and Y experiences magnetic force Fy.

What is the ratio Fx/Fy if the kinetic energy of X is half that of Y ?

a) 1/4
b) 1/2
c) 1/root 2
d) 1
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Just quoting in Puddles the Monkey so she can move the thread if needed
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(Original post by Puddles the Monkey)
x
3. C, half of 1/2mv^2 with constant mass (as both electrons) means that velocity is reduced by a factor of 1/sqrt(2)
4. (Original post by 16characterlimit)
C, half of 1/2mv^2 with constant mass (as both electrons) means that velocity is reduced by a factor of 1/sqrt(2)
but it says the ratio of the forces not the ratio of the velocity
5. (Original post by civ1)
but it says the ratio of the forces not the ratio of the velocity
My mistake, luckily since F=Bqv

Fx/Fy = Bqv/Bq(v/sqrt(2)) = 1/sqrt(2)

So still C.

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