Question

A ball is thrown into the air. Its height
h
from the ground, in meters, after
t
seconds is given by the equation below.

h
=
5
+
40
t
−
4.9
t
2

What is the average speed of the ball between 1 and 3 seconds after it is thrown?

A.
32.7 meters per second

B.
40.8 meters per second

C.
20.4 meters per second

D.
27.0 meters per second

Answer 1

Average rate of change = (h(3) − h(1)) / (3 − 1).

h(3) = 5 + 40(3) − 4.9(3)^2 = 5 + 120 − 44.1 = 80.9
h(1) = 5 + 40(1) − 4.9(1)^2 = 5 + 40 − 4.9 = 40.1

Average speed = (80.9 − 40.1) / 2 = 40.8 / 2 = 20.4 m/s

Answer: C.