A Hose pipe which disposes water at the speed of `20 m//s`. A very high building is no fire. Safe distance from building on ground is `8m`. How high can this water strike the building?

Explanation

We have to project water achieving max.y for given `x=8 m`
This can be solved by using equation of trajectory by putting `x=8` m and maximizing y by varying `theta`.
By `y=x tan theta-(gx^(2))/(2u^(2) cos^(2) theta)` Here `x=8m, u=20 m//s`
`y=8 tan theta-(10xx64(1+tan^(2) theta))/(2xx400)`
`0.8 tan^(2) theta-8 tan theta+(y+0.8)=0`
for `theta` real `b^(2)-4xx0.8(y+0.8) ge 0`
`y_("max")=19.2 m`