A fighter plane is flying horizontally at an altitude of 1.5 km with speed `720 kmh^(-1)`. At what angle of sight (w.r.t horizontal) when the target is seen, should the pilot drop the bomb in order to attack the target? `(Take g=10ms^(-2))`

Explanation

Consider the adjacent diagram. Let a fighter plane, when it be at position P, drops a bomb to hit a traget T.
Let `ltP'PT=theta`
Speed of the plane `=720 km//h=720xx(5)/(18)m//s=200m//s`
Altitude of the plane (P'T)=1.5km=1500m
If bomb hits the target after after time t, then horizontal distance travelled by the bomb,
`PP'=uxxt=200t " " ...(i)`
Vertical distance travelled by the bomb,
`P'T=(1)/(2)"gt"^(2) rArr 1500=(1)/(2)xx9.8t^(2)`
`rArr " " t^(2)=(1500)/(4.9) rArr t=sqrt((1500)/(49))=17.49 s`
Using value of t in Eq. (i),
`P P'=200xx17.49m`
Now, `" " tan theta=(P'T)/(P'P)=(1500)/(200xx17.49)=.49287=tan 23^(@) 12'`
`theta=23^(@) 12'`