The engine of a model rocket accelerates the rocket vertically upward for 2.0 s as follows: At t = 0, the rocket's speed is zero; at t = 1.0 s, its speed is5.0 m/s; and at t = 2.0 s, its speed is 18 m/s. Plot a velocity vs. time graph for this motion, and use the graph to determine each of the following.

(a) the rocket's average acceleration during the 2.0 s interval

m/s2

(b) the instantaneous acceleration of the rocket at t = 1.5 s

m/s2