In: Physics
A spaceship travels at 0.8c relative to Earth, and is able to fire projectiles at 0.6c relative to the spaceship. (a) If the spaceship moves towards Earth and fires the projectile directly towards Earth, how fast do observers on Earth see the projectile approaching? (b) If the spaceship moves away from Earth and fires the projectile directly towards Earth, how fast is the projectile moving relative to Earth? Is it approaching Earth or moving away from Earth? (c) The spaceship is passing by the Earth at a distance of a few light-minutes. The spaceship fires the projectile towards Earth and perpendicular to its current direction of travel. What is the speed of the projectile relative to Earth? What is the direction of the projectile as seen by Earth?