Question

man can swim at the rate of 5km/hr in still water. a river 1km wide flows at the rate of 3km/hr. a swimmer wishes to cross the river straight.Along what direction must he strike. what should be his resultant velocity. how much time he would take to cross.

Answer 1

please mark brainliest

Answer 2

Answer:

Explanation:

A.Velocity of man with respect to river water, `v = 5 km h^-1`. This is greater than the river flow velocity. Therefore, he can cross the river directly (along the shortest path or no drift condition from flow velocity). The angle of swim,

`theta = (pi)/(2) + sin^-1 ((u)/(v))`

=`90^@ + sin^-1 ((u)/(v))`

=`90^@ + sin^-1 ((3)/(5)) = 90^@ + 37^@ = 127^@` w.r.t. the river flow

or `37^@` w.r.t. perpendicular in upstream direction.

.

(b) Resultant velocity or velocity of mass will be

`v_m = sqrt(v^2 - u^2) = sqrt(5^2 - 3^2) = 4 k=km h^-1`

In the direction perpendicular to the river flow.

( c) time taken to cross the river

`t = (d)/(sqrt(v^2 - u^2)) = (1 km)/(4 km h^-1) =(1)/(4) h = 15 min`.