Question

95. A man swims to and fro along the bank of a river with a
velocity v relative to water. If the velocity of flow is u, the
average speed of the man (for to and fro motion) is:
(a) 0
(b) Vuv
? – u²
u+v
(c)
(d)
2
V-u2/v​

Answer 1

Answer:

v^2-u^2

v

Explanation:

Speed of river, u

Speed of man relative to water ,v

Downward speed of man w.r.t ground, v+u

Upward speed of man w.r.t ground, v−u

Downward time, t1= v+u

s

and upward time t2= v-u

s

Average speed = Total distance

Total time taken

Average speed , Av = s+s

s + s

v+u v-u

Hence, average speed is = v^2 - u^2

v