Question
Two seconds after projection a projectile is travelling in a direction inclined at 30∘ to the horizontal after one more sec, it is travelling horizontally, the magnitude and direction of its velocity are
Answer: Option B
:
B
Let in 2 sec body reaches upto point A and after one more sec upto point B.
Total time of ascent for a body is given 3 sec i.e. t=usinθg=3
∴usinθ=10×3=30.............(i)
Horizontal component of velocity remains always constant
ucosθ=vcos30∘..........(ii)
For vertical upward motion between point O and A
vsin30∘=usinθ−g×2[Usingv=u−gtvsin30∘=30−20[Asusinθ=30]
Substituting this value in equation (ii) u coa θ=20cos30∘=10√3......(iii)
From equation (i) and (iii) u=20√3andθ=60∘
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:
B
Let in 2 sec body reaches upto point A and after one more sec upto point B.
Total time of ascent for a body is given 3 sec i.e. t=usinθg=3
∴usinθ=10×3=30.............(i)
Horizontal component of velocity remains always constant
ucosθ=vcos30∘..........(ii)
For vertical upward motion between point O and A
vsin30∘=usinθ−g×2[Usingv=u−gtvsin30∘=30−20[Asusinθ=30]
Substituting this value in equation (ii) u coa θ=20cos30∘=10√3......(iii)
From equation (i) and (iii) u=20√3andθ=60∘
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