35. Special Relativity

Jill can throw a ball at a speed of 80mph, consistently, on the ground. She gets into the back of a truck, which drives down the road in the $+x\text{-direction}$ direction at 30mph. Jill faces the back of the truck and throws a ball. According to Galilean relativity, what is the $x\text{-component}$ component of the velocity of the ball relative to the ground?

Sam is cruising in his spaceship moving at$0.9c$. Suzy is directly in front of Sam and is at rest. Suzy flashes her headlights at Sam, hoping he will slow down. According to Sam, how fast is the light from Suzy's headlights moving as it approaches him?

Olive the astronaut is flying her spaceship back home to earth at $0.9c$. Her spaceship has lights on it; one at the front of her ship, and one at the back of the ship. Olive notes that the two lights flash simultaneously. Are they simultaneous according to an Earth-based observer? If not, which one blinked first?