NCERT Class 11 Physics Solutions: Chapter 4 – Motion in a Plane Part 6

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Question 4.14:

In a harbor, wind is blowing at the speed of 72 km/h and the flag on the mast of a boat anchored in the harbor flutters along the NPE 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?


Velocity of the boat,

Velocity of the wind,

The flag is fluttering in the north-east direction. It shows that the wind is blowing toward the north-east direction. When the ship begins sailing toward the north, the flag will move along the direction of the relative velocity (vwb) of the wind with respect to the boat.

Figure shown the condition of examples.

Figure 4.14

Loading Image

The angle between and

Angle with respect to the east direction

Hence, the flag will flutter almost due east.

Question 4.15:

The ceiling of a long hall is 25 m high. What is the maximum horizontal distance that a ball thrown with a speed of can go without hitting the ceiling of the hall?


Speed of the ball, u

Maximum height, h

In projectile motion,

The relation gives the maximum height reached by a body projected at an angle θ:

Horizontal range R