Week 6, clip 7

Timepoint:  06:52.7

1) Cosmic rays include electrons and other particles accelerated to close to the speed of light.  Consider an electron accelerated to 40% the speed of light.

Using the relativistic expression for momentum, what is the total momentum in this electron?  Give your answer in kg*m/s, rounded to two significant digits.  

Answers:
1) The accepted range is [1.1e-22,1.3e-22]

Explanation:
The velocity is 0.4 c.  
The mass is 9.109382e-31 kg.
Plugging into the equation p = (m*v) / ((1 - (v/c)^2)^0.5), we get 
p = (9.109382e-31 * (0.4 * 2.9979e8)) / (1 - (0.4)^2)^0.5) = 1.189e-22 kg*m/s