afrazer721
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- Feb 1, 2012
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A physicist has determined that the altitude h in feet of a rocket t seconds after firing is given by
h=-16t^2+96t. Find how long the rocket will take to (a) reach a height of 144 feet, (b) hit the ground. Work out steps to answer, please.
(a) Let h=144 so, 144=-16t^2+96t
Convert to standard form: 16t^2-96t+144=0
We have (4t-12)(4t-12)=0, so that 4t-12=0
4t =12
t = 3 seconds.
(b) The negative sign indicates that gravity is acting to decrease the height of the rocket, pulling it downward.
This means that the height is zero.
I want to know how long will it take for the rocket to hit the ground?
Re-arrange terms: 96t=16t^2
96 =16t^2/t
96 =16t
t=6 seconds.
h=-16t^2+96t. Find how long the rocket will take to (a) reach a height of 144 feet, (b) hit the ground. Work out steps to answer, please.
(a) Let h=144 so, 144=-16t^2+96t
Convert to standard form: 16t^2-96t+144=0
We have (4t-12)(4t-12)=0, so that 4t-12=0
4t =12
t = 3 seconds.
(b) The negative sign indicates that gravity is acting to decrease the height of the rocket, pulling it downward.
This means that the height is zero.
I want to know how long will it take for the rocket to hit the ground?
Re-arrange terms: 96t=16t^2
96 =16t^2/t
96 =16t
t=6 seconds.
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