Question

A boy runs away from a pole in a straight line so
that its velocity is inversely proportional to the
distance from the pole. When boy is at a point A at
a distance x = 100 m from the pole, its velocity is
V = 2 m/s. What time will boy take to run away
from point A to point B which is at a distance
X2 = 200 m from the pole?
(1) 50 S
(2) 60 s
(3) 75s
(4) 90 s​

Answer 1

Explanation:

velocity at 100 m is 2 m/s

therefore , velocity at 200 m is 1m/s

v^2 -u^2 =2as

1 -4 =2×a×100

therefore a = -3/200

it is deceleration

s =ut+ 1/2at^2

100 = 2t + 1/2× (-3/200) ×t^2

so t = 200

Answer 2

Answer:

ans.below

Explanation:

v = velocity , s = distance

v = a/x

dx/dt =a/x  

xdx = adt

∫xdx = ∫adt

x²/2 = at + b

x² = kt + c

a = vx = 200 , k = 2a = 400 = k , c = 0

t = √x/k = √200/400 = √1/2