Question

A ball is thrown upward from the top of a building. The function below shows the height of the ball in relation to sea level, ft, in feet, at different times t in seconds:

f(t) = -16t2 + 34t + 80

The average rate of change of f(t) from t = 5 seconds to t = 7 seconds is _____ feet per second.

Answer 1

Well I worked the problem out and I got -158 but i dont think thats right because when i put it in a graphing calculator the rate of change was much greater

Answer 2

because t=5 seconds would be -150 and t=7 seconds would be -465

Answer 3

@jim_thompson5910

Answer 4

@dan815

Answer 5

or @OOOPS do you think you could help me?

Answer 6

So you think i should put -157.5 rather than -158? and doesnt the minus sigh mean that it is still going down?

Answer 7

Sign*

Answer 8

Well once the line goes past 0 in the y axis wound that already consider it under the ground?

Answer 9

redo, please, it is "sea level"

Answer 10

It is possible if it is under the sea level.

Answer 11

sure :p

Answer 12

OK, since when y =0, that is the ball touch the surface of the sea, at that moment, t = 3.54

Answer 13

Well if the sea level starts at x=0 the touch of the ball would be 80 feet over sea level

Answer 14

But it can't be done since the speed of the ball is reduced by the pressure of the water also. Ha!!! it 's interesting.

Answer 15

@perl @jim_thompson5910

Answer 16

@freckles @zepdrix

Answer 17

Okay wait the sea level is just an act of measurement... It's just pretend if the ball could go straight through water without being slowed down.... Just forget the whole ball part in general.. Just think of it as a graph.. So we know where t=5 and t=7 is so we need to just find the average rate of change between those two points.

Answer 18

If ignore everything, then you are correct.

Answer 19

So the answer would be -158?

Answer 20

\(\dfrac{-465-(-150)}{2}=-157.5\)

Answer 21

So do you think i should round 157.5 to 158?

Answer 22

nope. just let it as it is

Answer 23

ugh idk what i should make it... Im nervous that if i make it 157.5 ill get it wrong but now im nervous if i do 158 ill get it wrong too xD

Answer 24

hahaha.. ok, wait for other's opinion.

Answer 25

it doesnt say anywhere that i should round to the nearest whole number or anything so i believe i should just leave it as it is

Answer 26

Since it is important to you, I dare not say anything which can take you down. I am sorry. Good luck. I go to bed now.

Answer 27

Haha thanks for the help! :D

Answer 28

i did get it wrong but i still got a 90 so its not a huge deal... So i believe the answer would be 158 :D thank you so much for the help @OOOPS