Question 4.14 In a harbour, wind is blowing at the speed of 72 km/h and the flag on the mast of a boat anchored in the harbour flutters along the N-E direction. If the boat starts moving at a speed of 51 km/h to the north, what is the direction of the flag on the mast of the boat?
Chapter Motion In A Plane Page 87
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Direction of blowing of wind is along N-E direction due to flag flutters along N-E direction.
Velocity of boat = 51 km/h ( North direction )
The flag will flutter along the direction of the relative velocity of wind with respect to boat.
Angle between Vw and - Vb = 45° + 90° = 135° .
Let ∅ is the angle Between relative velocity of wind wrt boat (Vwb ) and velocity of wind .
Use , formula ,
Tan∅ = Vbsin135°/( Vw + Vbsin135°)
= 51sin135°/(72 + 51sin135°)
= 51 × 1/√2/(72 -51/√2)
= 51/(72√2 - 51)
= 1.0034 ≈1
Hence, ∅ = 45° ( approximately )
Hence, the flag will flutter almost due to East .
Velocity of boat = 51 km/h ( North direction )
The flag will flutter along the direction of the relative velocity of wind with respect to boat.
Angle between Vw and - Vb = 45° + 90° = 135° .
Let ∅ is the angle Between relative velocity of wind wrt boat (Vwb ) and velocity of wind .
Use , formula ,
Tan∅ = Vbsin135°/( Vw + Vbsin135°)
= 51sin135°/(72 + 51sin135°)
= 51 × 1/√2/(72 -51/√2)
= 51/(72√2 - 51)
= 1.0034 ≈1
Hence, ∅ = 45° ( approximately )
Hence, the flag will flutter almost due to East .
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Answer: Wind is blowing along the north- east and boat is at rest this time So, head of the flag is also in direction of wind. Now,when boat starts moving with certain velocity along the north direction head of the flag started to twist towards the east direction.
Explanation:
Explanation:
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