Question

If the kinetic energy of an electron is 4.1e-18 j, what is the speed of the electron? (you can use the approximate (nonrelativistic) formula here.)

Answer 1

The kinetic energy of the electron is

`K= (1)/(2)mv^2`
where
`m=9.1 \cdot 10^(-31) kg` is the mass of the electron and v its speed. Since we know the value of the kinetic energy,
`K=4.1 \cdot 10^(-18) J`, we can find the value of the speed v:

`v= \sqrt{ (2K)/(m) }= \sqrt{ (2\cdot 4.1 \cdot 10^(-18)J)/(9.1 \cdot 10^(-31)kg) } = 3\cdot 10^6 m/s`