Question
A ladder 5 m long is leaning against a wall. The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2 cm/s. How fast is its height on the wall decreasing when the foot of the ladder is 4m away from the wall?
Solution
Let the foot A of the ladder be at a distance x metres from the wall and y metres be the height of the wall at any time t.
Differentiating both sides w.r.t. 't', we get,
(given)
