The rocket will be at the height of 450metres at 13.16secs and 6.84secs
Given the expression modeled by the height S(t)=-5t^2+100t where
t is the time taken by the rocket to take off
s is the height traveled by rocket
In order to find the height of the rocket 7 seconds after it takes off, we will substitute t = 7 into the equation
S(7) = -5(7)²+100(7)
S(7) = -5(49)+700
S(7) = -245+700
S(7) = 455metres
Hence the height of the rocket 7 seconds after it takes off is 455metres
Given that S = 450m, we can also get the time taken by the rocket at this height.
Recall that S(t)= -5t²+100t
450 = -5t²+100t
Rearrange
-5t²+100t - 450 = 0
5t²-100t + 450 = 0
Divide through by 5
t²-20t + 90 = 0
On factorizing above equation;
t= 10+√10 or t=10−√10
t = 10+3.1623 or 10 - 3.1623
t = 13.16 and 6.84secs
Hence the rocket will be at the height of 450metres at 13.16secs and 6.84secs
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