Question

How much work is required to stop an electron (m=(9.11x10^-31)kg) which is moving with a speed of (1.100x10^6) m/s? First significant figure of answer is 5.00x10^-19 J

Answer 1

Solution

As the electron is in the motion so it has Kinetic energy.

To make the electron stop from motion we need to do a work which will make its kinetic energy zero.

So Work done = Final KE - Initial KE

W = 0 - (MV² )/2

replacing the value in the equation.

W = - (9.1 x 10 ^-31 x 1.1 x 1.1 x 10⁶⁺⁶) /2

W = -5.50 x 10^-19 Joule

the work is negative as the KE is decreased. You can take the value as 5.0 eV (electron volt a unit of energy )