Question

a model rocket is launched from a raised platform at a speed of 144 ft./s it's height in feet is given by h(f)= -16t squared plus 144 t+20 (t=seconds after launch) After how many seconds does the object reach its maximum height

Answer 1

$h(t)=-16t^2+144t+20$

$\frac{dh(t)}{dt}=0\to -32t+144=0\to t=144/32=4.5(s)$

After $4.5 (s)$.