Question

A boat moves relative to water with a velocity which is 'n' times the river flow
1) IF n<1 boat con not cross the river
2) IF n=1 boat can not cross the river without drifting
3) IF n>1 boat can cross the river along shortest path
4) Boat can cross the river what ever is the value of n excluding zero value
A) only 1 is correct
B) 1 and 2 are correct
C) 3&4 are correct
D) 2,3and 4 are correct
A
B
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Answer 1

Step-by-step explanation:

In this case, the velocity of boat is less than the river flow velocity. Hence, boat cannot reach the point directly opposite to its starting point, i.e., drift can never be zero. <br> Suppose the boat starts at an angle

from the normal diraction up stream as shown in (Fig. 5.90). <br> Component of the velocity of boat along the river, <br>

<br> and velocity perpendicular to the river,

<br> time taken to cross the river is

<br> Drift

<br> The drift

is minimum when

<br> or

<br> or

<br> i.,e., for minimum drift, the boat must move at an angle