Question

A football is thrown into the air. The height, h(t), of the ball, in metres, after t seconds is modelled by h(t) = -4.9(t-1.25)^2+9
(a) how high off the ground was the ball when it was thrown? I say the answer is 9. Is this correct?
(b) What was the maximum height of the football? - need help with this one...
(c) Is the football in the air after 6 seconds?
(d) when does the ball hit the ground?

Answer 1

h(t) = -4.9(t-1.25)^2+9
gives the height at any time
what is the value of h(t) at t=0 (right when the ball is thrown)?

Answer 2

ah you got that. yes correct.

Answer 3

maximum height...: several ways you can find this. Are you in calculus?

Answer 4

no - just using functions in gr 11 math

Answer 5

ok, the vertex formula maybe then? are you familiar with finding the vertex of a parabola?

Answer 6

yes

Answer 7

or... you can just plot it on your calculator/ plotting software... and trace to the vertex... depends on the assignment.

Answer 8

ok, what did you get? I'll check it.

Answer 9

whoops, didn't look closely enough at your expression... looks like you'll need to expand it to find the answer to a)

Answer 10

-4.9 t^2 +12.25 t +1.34375

Answer 11

height when t= 0 is 1.34375

Answer 12

yes - i got that for question (c). Thanks!

Answer 13

how do i find the maximum height of the football?

Answer 14

vertex formula

Answer 15

http://www.purplemath.com/modules/sqrvertx.htm

Answer 16

it's already set up for you, basically.

Answer 17

great - now (c) after 6 seconds = when i substitute that into the equation - i get -101.55625 which means the football was not in the air at 6 seconds?

Answer 18

right.