Question
a man of height 2 meter walk at a uniform speed of 5km/hr away from a lamp post which is 6 meter high find the rate at which length of his shadow increase
Answers
Reiny
Make your sketch showing the man at some position.
let the distance he is from the post be x,
let the length of his shadow by y
you have similar triangles, so we have:
6/(x+y) = 2/x
2x + 2y = 6x
y = 2x
dy/dt = 2dx/dt
= 2(5) km/hr
let the distance he is from the post be x,
let the length of his shadow by y
you have similar triangles, so we have:
6/(x+y) = 2/x
2x + 2y = 6x
y = 2x
dy/dt = 2dx/dt
= 2(5) km/hr