# physics

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How much work must be done to increase the speed of an electron from 0.200c to 0.210c? In (MeV)

• physics -

The energy is given by E = gamma m c^2. Take the difference of this for
v= 0.210c and 0.200 c

• physics -

CountIblis is correct.

gamma is 1/sqrt[1 - (v/c)^2]

gamma changes from 1.0206 to 1.0461

Multiply the difference by the rest mass energy.

• physics -

is rest mass energy

9.11e-31 * (3e8)^2 ??

and do I need to convert from J to ev to KeV?

Thanks for the help

• physics -

Yes, that is the rest mass energy in Joules.

Since they do ask for the answer in MeV, use the conversion factor
1 MeV = 1.602*10^-12 J

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