Question

a man of height 1.5m walks towards a lamp post of height 4.5m at the rate of 3/4m/sec find the rate at which the shadow is shortening and tip of shadow is moving. PL PL ans this question​ I WILL MARK BRAINLIEST AND FOLLOW BACK

Answer 1

Given : a man of height 1.5m walks towards a lamp post of height 4.5m at the rate of 3/4m/sec

To find : the rate at which the shadow is shortening and tip of shadow is moving

Solution:

Lamp post Height = 4.5 m

Height of Man  =  1.5  m

Distance of Person from base of Lamp post  = D m

Length of Shadow = L  

Then   1.5/4.5    =  L/(D + L )

=> D+ L = 3L

=> D = 2L

=> L = D/2

Distance of tip of shadow =  D + D/2 = 3D/2   m

Man is walking at the rate of 3/4 m/sec

dD/dt  =  -3/4

L = D/2

dL/dt = (1/2)dD/dt =  (1/2)(-3/4)  = -3/8

-ve sign shows shortening

=> Length of shadow is shortening at the rate of  3/8 m/s

Distance of tip of shadow =  3D/2    = 3(3/4) =  9/8 m/s

Distance of tip of shadow  is moving at the rate of 9/8 m/s

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Answer 2

Answer:

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