A river `400 m` wide is flowing at a rate of `2.0 m//s.` A boat is sailing at a velocity of `10.0 m//s` with respect to the water In a direction perpendicular to the river.
(a) Find the time taken by the boat to reach the opposite bank.
(b) How far from the point directly opposite to the starting point does the boat reach the opposite bank?

Options

A. `40 sec,80 m`
B. `30 sec,40 m`
C. `20 sec,20 m`
D. `35 sec,80 m`

Answer

A

Explanation

As it is given that boat is sailing in a direction normal to current. Crossing velocity of boat is `=10 m//s`. So time taken by the boat to reach the other bank is `400/10=40s`.Drift due to flow of river is = Drift velocity `xx` time to cross the river Here boat is sailing in normal direction so direction so drift velocity is the river current velocity.Thus, drift is `x=2.0xx40=80m`