Question

Q2) The graph shows the speed of a firework shell during a flight of 20 seconds:

250
200
150
(s/u) paads
100
50
O
2
4
6
8
10
12
14
16
18
20
Time (s)
a) Work out the rate of change during the first 4 seconds.
b) Work out the rate of change between 8 seconds and 12 seconds.

Answer 1

a. 37.5

b. 25

Explanation:

a. Rate of change the first 4 seconds can be calculated using the points (0, 0) and (4, 150):

Rate of change =
`(y_2 - y_1)/(x_2 - x_1) = (150 - 0)/(4 - 0) = (150)/(4) = 37.5`

b. Rate of change between 8 seconds and 12 seconds using the points (8, 150) and (12, 250):

Rate of change =
`(y_2 - y_1)/(x_2 - x_1) = (250 - 150)/(12 - 8) = (100)/(4) = 25`