# Length contraction & relativistic momentum, mass and energy

##### Intros
###### Lessons
1. Length Contraction & Relativistic Momentum, Mass and Energy
2. Introduction to length contraction
3. Relativistic Momentum, Mass, and Energy
4. Relativistic Addition of Velocities
##### Examples
###### Lessons
1. A star is 62 light-years away in the Earth frame of reference. How fast would you have to travel so that to you the distance is only 15 light-years?
1. Suppose you decided to travel to a star 60 light-years away at a speed that tells you the distance is only 15 light-years. How many years would it take to make the trip?
1. At what speed will the length of a 1.00m stick look 20.0% shorter?
1. The length of a ruler placed in spaceship in 32cm. The spaceship moves with a speed of 0.080c. what would be the percent decrease in the length of the ruler?
1. What is the relativistic momentum of an antiproton moving at a speed of 0.68c and mass of 1.674 x 10-27 kg?
1. What is the percentage change in the momentum of an electron that accelerates from 0.25c to 0.80c? (mass of electron = 9.12 x 10-31kg)
1. Calculate the rest energy of an electron in joules and in Mev
(1Mev= 1.60 x 10-13J)
1. What would be the momentum and kinetic energy of a proton travelling with a speed of 1.80 x 108m/s. (Proton rest mass = 1.67 x 10-27kg)
1. Calculate the kinetic energy and momentum of a proton travelling 6.24 x 107m/s. What would be the percentage error if the value was calculated using classical formula?
1. A person on a spaceship traveling at 0.60c (with respect to the Erath) observers a comet come from behind and pass her at a speed of 0.60c. how fast is the comet moving with respect to the Earth?
1. A spaceship leaves the Earth traveling at 0.61c. A second spaceship leaves the first at a speed of 0.77c with respect to the first one. Calculate the speed of the second spaceship with respect to the earth if it is fired
1. In the same direction the first spaceship is already moving
2. Directly backwards towards the Earth