Problem 14.

  Each of the protons in a particle beam has a kinetic energy of . What are the magnitude and direction of the electric field that will stop these protons in a distance of 2 m?

Solution

To stop the proton the direction of electric field should be opposite to the direction of the beam.

To find the magnitude of electric field we need to write down the energy conservation: the initial energy ( K ) of proton should be equal to the work done by an electric field:

Where . From this equation we can find electric field: