Video Problem #1, Lecture #13: (a) A particle has an energy of 20 MeV and a momentum of 5 MeV/c. What is its mass? (b) The same particle is viewed by a passing spaceship. From the perspective of the ship, the particle has an energy of 30 MeV. What is the mass of the particle as measured by people on this ship? (c) What is the momentum of the particle as measured by people on the ship?