Question

vertical cossponent of velocing
( v_{4}=v sin theta )
( N O_{0} O, quad u sin y quad S=u+1 frac{1}{2} a t^{2} )
here ( , y=u_{y} t+frac{1}{2} a y t^{2}left(because a_{y}=yright) )
( o r, y=V sin theta t-frac{1}{2} g t^{2} )
After pusting ( t=1 ) sec then ( (y=11) ) ( h=v sin theta-frac{1}{2} g-r(hat{theta}) )
again ils we puf ( t=3 ) sec then ( y=h ) ( h=3 v sin theta-frac{9}{2} g r )
from
(1) and
( widehat{C i} )
[
2 v sin theta=4 g
]
now, time of blight? ( T=frac{2 v sin theta}{j} )
[
2 frac{9 g}{0}=4 sec
]
oppion ( ()

# A projectile is thrown with velocity v making an angle o with the horizontal. It just crosses the top of two poles, each of height h, after 1 second and 3 second respectively. The time of flight of the projectile is (A) 1 S (B) 3 s (0) 4 s (D) 7.8

Solution