A proton in an accelerator attains a speed of 0.772c. what is the magnitude of the momentum of the proton?

Momentum can be calculated using the following rule:

momentum = mass x velocity

For this proton we have:

mass of proton is a constant = 1.67 x 10^-27 kg

velocity = 0.772 c where c is the constant speed of light

velocity = 0.772 x 3 x 10^8 = 231.6 x 10^6 m/sec

Substitute with the mass and velocity to calculate the momentum as follows:

momentum = 1.67 x 10^-27 x 231.6 x 10^6 = 3.86772 x 10^-19 kg. m/sec