Relative Motion

Question

Swimmer speed relative water 2 m/s; river speed 1 m/s. Width 100 m. Minimum crossing time is:

RankGuru · Accepted Answer

To cross the river in minimum time, the swimmer must swim directly perpendicular to the river current (parallel to the width). 
The time taken to cross is determined only by the component of velocity perpendicular to the river banks ($v_y$).
$t_{min} = \frac{	ext{Width}}{v_{swimmer}} = \frac{100 	ext{ m}}{2 	ext{ m/s}} = 50 	ext{ s}$.
Note: While the swimmer will be carried downstream (drift) by the river current, this does not affect the time required to cover the $100 	ext{ m}$ width.

Rank Guru

Relative Motion

Select the correct option:

Solution

🔒 Solution Hidden from View

More relative motion Practice Questions

Rain falls vertically with speed 12 m/s. A person runs east at 4.36 m/s and observes the rain at 20°...

Two trains approach each other at 40 km/h and 60 km/h. Relative speed is:

Boat velocity 4 m/s north, current 3 m/s east. Resultant speed magnitude is:

Rain falls vertically at 6 m/s. Person runs east at 8 m/s. Relative velocity components of rain w.r....

Two cars A and B are moving with velocities 10 m/s and 20 m/s respectively in the same direction. Ca...

About This Question