Question

A stone is launched vertically upward from a cliff 96 ft above the ground at a speed of 80 ft/s. its height above the ground "t" seconds after the launch is given by s= -16t^2+80t-96 for 0 13 years ago

Answer 1

Find the derivitive, set it equal to 0 and solve. The second derivitive will be negative if it is a maximum.

Answer 2

s'

Answer 3

s' = -32t +80
s'' = -32

Answer 4

is that the answer? @sthop456

Answer 5

not yet. you must solve 0 = -32t +80

Answer 6

we have s=f(T) therefor maximising it by putting ds/dt =0 we obtain t=2.5s and putting it back in the function we can obtain the required height....=4units

Answer 7

@Study23 so -32t=-80, t=2.5

Answer 8

exactly....

Answer 9

@kunal so it'd reach maximum in 4 seconds?

Answer 10

@sthop456 is it 4 then? lol

Answer 11

2.5

Answer 12

kunal says it's 4 if you plug it back to it's original equation?

Answer 13

It'll reach 4ft max height in 2.5 secs.

Answer 14

ok, thanks :)