Question

A man is trying to cross a river flowing a
a speed of 5 ms 1 to have least possible
displacement by swimming at an angle of
143° to the stream. The drift he suffers
when he is crossing the same river in least
possible time is (Width of river = 1 km)
​

Answer 1

Answer:

Explanation:

=> A man is trying to cross a river flowing a  speed of 5 ms 1 to have least possible  displacement by swimming at an angle of  143° to the stream.

(∴ θ = 143° - 90° = 53°)

∴ U sin θ = 5

U 4/5 = 5

U = 5 * 5 / 4

= 25 / 4

=> But, the drift he suffers  when he is crossing the same river in least  possible time is (Width of river = 1 km)

Speed of river, v = 5

Width of river, w = 1 km = 1000 m

Δx = v * w / u

= 5 * 1000 / 25/4

= 5000 * 4 / 25

= 800 m

=> When man is crossing the river in least  possible time is:

T = w/u

= 1000/25/4

= 4000/25

= 160s

Answer 2

see these pics my friends

please give me like

& 4 stars