15.22: Momentum
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The linear momentum \bf{p} of a body, referred to a frame \Sigma, is defined as
\bf{p} = m\bf{u}. \label{15.22.1}
Here m and \bf{u} are its mass and velocity referred to \Sigma. Note that m is not the rest mass.
The rest mass of a proton is 1.67 % 10-27 kg. What is its momentum referred to a frame in which it is moving at 99% of the speed of light?
Answer = 3.51 % 10-18 kg m s-1.