Question

A boat moving perpendicular to the bank with a velocity of $7.2$ km/h. The current carries it $150$m downstream, find the velocity of the current.(The width of the river is $0.5$ km).

• A. $0.4m{s}^{-1}$
• B. $1.2m{s}^{-1}$
• C. $0.5m{s}^{-1}$
• D. $0.6m{s}^{-1}$

Answer 1

The correct option is D $0.6m{s}^{-1}$

Width of river $d=0.5km$

Velocity of boat perpendicular to the river current $v=7.2km/h$

So,, time taken to cross the river $t=\frac{d}{v}=\frac{0.5}{7.2}hr=\frac{0.5}{7.2}\times 3600=250s$

Drift of the boat $x=150m$

So, velocity of current $V_R=\frac{x}{t}=\frac{150}{250}=0.6m/s$