Question

A person reaches a point directly opposite other bank of a river. The velocity of the water in the river is 4 ms and the velocity of the person in still water is 5 ms. If the width of the river is 84.6 m, time taken to cross the river in seconds is on the -1 (a) 28.2 (b) 9.4 (c) 2 (d) 84.6

Answer 1

Explanation:

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v = final velocity

u = initial velocity

s = Distance

a = Acceleration

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✨ First case,

v = 0 m/s

u = 10 m/s

s = 20 m.

➡️ v^2 = u^2 + 2as

Or, 0 = 100 + 40a

Or, a = - 100 /40 = - 5/2.

.°. a = - 5/2 m/s^2

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✨Second case,

v = 0 m/s

u = 20 m/s

a = - 5/2 m/s^2

➡️ v^2 = u^2 + 2as

Or, 0 = 400 - 5s

Or, s = 400/5 = 80.

.°. The stopping distance will be 80 m.

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Thanks..