Question from some tutorial:
A light shines from the top of a lamp post 15 m high. A ball is dropped from the same height from a point 9 m away from the light. It is known that the balls falls a distance s = 4.9t2 m in t seconds. Find the speed of the shadow of the ball on the ground 0.5 second later.
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Answer:
Let x be the distance of the shadow from the lamp post.
Differentiate implicitly with respect to t
Also,
When t = 0.5, s = 1.225, x = 110.20408, ds/dt = 4.9
Sub into equation
Hence, dx/dt = -440.8 ms-1
Speed of shadow = 440.8 ms-1
