A man is running along a circular track has a speed of 10 kmph. A source of light is at the center of the circular track. A wall along the tangent from which he starts. what is the speed of the shadow of the man on the wall when he covers 1/8 th of the track.

Dear ANAM

from the figur when man is at point P shadow will be at point B

tanΘ =x/r

 x =r tanΘ

differentiate

dx/dt = r sec²Θ dΘ/dt

          =r sec²Θ * W      where w is angular velocity

          =v sec²Θ

at 1/8 th of the track it will cover an angel  π/4

so dx/dt = 10* 2 =20 kmph

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