=4s ∴ In 2s , it will be at the topmost point, where it will hit the hillside. After 2s, the maximum height (Hmax) AB=Hmax=
u2sin2θ
2g
=
402sin230∘
2×10
=
1600×1
2×10×4
=20m Also, at this time the horizontall distance travelled will be half of the range =OA i.e
R
2
OA=
R
2
=
u2sin2θ
2g
=
402sin(2×30∘)
2×10
=
1600sin60∘
20
∴
R
2
=80
√3
2
=40√3 . ∴ The displacement from the projection point, OB=D=√OA2+AB2 (By Pythagorous theorem) ⇒D=√(40√3)2+(20)2=√4800+400=√5200 ⇒D=√4×13×100=2×10√13=20√13m