If a ball is thrown into the air with a velocity of 40 ft/s, its height in

Question:

If a ball is thrown into the air with a velocity of 40 ft/s, its height in feet seconds later is given by y = 40 t - 16t2.
(a) Find the average velocity for the time period beginning when t = 2 and lasting
(i) 0.5 second
(ii) 0.1 second
(iii) 0.05 second
(iv) 0.01 second
(b) Estimate the instantaneous velocity when t = 2.