Question

29. A man crosses a river of width 400 m flowing at
40 m/s in minimum time. If velocity of man in still
water is 50 m/s then the displacement of man
while he reaches the opposite bank of the river is
(1) 80 m
(2) 8/4 m
(3) 80/41m (4) 10/41m​

Answer 1

Thus the displacement while reaching the opposite bank of the river is 80 m.

Option (1) is correct.

Explanation:

A man crosses a river of width 400 m flowing at  2 m/s in minimum time. If velocity of man in still  water is 10 m/s then the displacement of man  while he reaches the opposite bank of?

Solution:

Width of river = 400 m

Swimming speed = 50 m/s

Time taken to cross the river = distance / speed = 400/10 = 40 s  

Horizontal displacement due to river speed = speed×time = 40×2 = 80 m

Thus the displacement while reaching the opposite bank of the river is 80 m