Problem 13. A rocket is fired vertically upwards with an initial speed of 80 m/s. It accelerates upwards at 4 m/s² until it reaches an altitude of 1000 m when

its engines fail and it is influenced only by the Earth's gravity. (a) How long is the rocket in motion? (b) What is its maximum altitude? (c) What is its speed just before it crashes back into the Earth? (d) Make qualitatively correct graphs of y, v and a versus t with all the time axes aligned.