Question

Boat travels upstream in a river and at t = 0 a wooden cork is thrown over the side with zero initial velocity. After 7.5 minutes the boat turns and starts moving downstream catches the cork when it has drifted 1 km downstream. Then the velocity of water current is ______.

Options

• 2 km/h

• 4 km/h

• 6 km/h

• 8 km/h

Answer 1

Boat travels upstream in a river and at t = 0 a wooden cork is thrown over the side with zero initial velocity. After 7.5 minutes the boat turns and starts moving downstream catches the cork when it has drifted 1 km downstream. Th en the velocity of water current is 4 km/h.

Explanation:

According to the problem,

V_w (7⋅5 + t) + 7⋅5(V_b – V_w)_B

= (V_b – V_w)t

Solving above at t = 7⋅5 min

V_w = 4km/h.