The rock will be 15ft above the ground 0.25 and 2.5secs after
The height of the rock above the ground is expressed according to the expression [tex]s(t)=-16t^2+44t+5[/tex]
In order to get the time the rock will be 15ft above the ground, we will substitute s(t) = 15 ft into the formula above;
[tex]15= -16t^2+44t+5\\-16t^2+44t = 15 -5\\-16t^2+44t = 10\\-16t^2+44t- 10 = 0\\16t^2-44t+10=0[/tex]
Factorize the expression to get the value of "t"
2(4t−1)(2t−5) = 0
4t - 1 = 0
4t = 1
t = 0.25secs
Similarly 2t - 5 =0
2t = 5
t = 5/2 = 2.5secs
This shows that the rock will be 15ft above the ground 0.25 and 2.5secs after
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