If a roller coaster has a mass of 50 kg when it is full of passengers, at what height will the coaster be moving at 4 m/s

The star betelgeuse is about 600 light-years away. if it explodes tonight, a. we'll know because debris from the explosion will rain down on us from space.b. we'll know it immediately because it will be brighter than the full moon in the sky.c. we won't know about it until 600 years from now.d. none of the above.