Question

A boat is sent across a river with a velocity of 8km/hr. If the resultant velocity of the boat is 10km/hr, then the velocity of the river is

Answer 1

howdy!!

your answer is----

let the velocity of river is Vr.

Given, velocity of boat Vb = 8km/h

and resultant velocity VR = 10km/h

since, angle between Vb and Vr is 90°

so , | Vr + Vb | = VR

==> √ 8^2 + Vr^2 + 2 VrVb cos ∅ = 10

==> √ 64+Vr^2 + 2 VrVb cos 90° = 10

==> 64 + Vr^2 = 100

==> Vr^2 = 100-64 = 36

==> Vr = √36 = 6km/h

hence, the velocity of river is 6km/h

hope it help you