Alex C.

asked • 12/13/16

Related rates sliding ladder

A 10m ladder is leaning against the vertical wall of a house. If the lower end of the ladder is being pulled horizontally away from the wall at the rate of 0.6m/s, how fast is the top of the ladder sliding down the wall when the lower end is 8m away from the wall? 
 
 
I just need to know if my answer is right. I ended up getting -0.8m/s

1 Expert Answer

By:

Alex C.

Why is it positive and not negative ?
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12/13/16

Gregg K.

tutor
Because I said sliding down , the word down would indicate the negative
 
It is moving down at .8m/s
 
Your question asks how fast is the ladder slidding DOWN the wall
 
 
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12/13/16

Gregg K.

tutor
the height of the top of the ladder (y) is decreasing with the ground as the reference point. That is why y ' is negative
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12/13/16

Gregg K.

tutor
If you simply asked what the rate of the top of the ladder was I would have said -.8 m/s
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12/13/16

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