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[Irokenics]

someone help me out here i soooo cant get this

A boy is flying a kite. If the kite is 60m above the ground and the wind is blowing it on a horizontal course at 8m/s, find how fast the boy is paying out the string when the kite is 100m from him

the answer is 6.4m/s

someone show me the working! it maybe easy but yerh i'm an idiot...

 

[Affinity]

let length of string as a function of time be L(t)

L = sqrt(h^2 + d^2)
where h is the height of the kite and d is the horizontal distance of the kite from the boy.

dL/dt = (dL/dd) * (dd/dt)
evaluated at their respective values.

dL/dt = d/sqrt(h^2 + d^2) * 8
= 80/100 * 8
= 6.4

My guess is.. you probably interpreted 100 as the horizontal distance, instead of the straight line distance