1. A ball is projected vertically upward from the top of a 15 m high building with an initial speed of 20 m s−1. Take the acceleration due to gravity acting downwards as 10 m s−2.
(a) Write a quadratic polynomial h(t) that gives the height (in metres) of the ball above the ground t seconds after it is thrown.
(b) Find the value(s) of t at which the ball reaches ground level.
(c) State which of the value(s) obtained in part (b) is physically meaningful and explain why.
(d) On a suitable set of axes, sketch the graph of y=h(t) for the relevant interval of t, showing clearly the y-intercept, the zero(s) and the approximate maximum height attained by the ball.