|May20-06, 05:24 PM||#1|
Stuck on couple related rates problems..
1. A ship with a long anchor chain is anchored in 11 fathoms of water. The anchor chain is being wound in at a rate of 10 fathoms/minute, causing the ship to move toward the spot directly above the anchor resting on the seabed. The hawsehole ( the point of contact between ship and chain) is located 1 fathom above the water line. At what speed is the ship moving when there are exatly 13 fathoms of chain still out?
For this problem I started with this drawing.. http://img.photobucket.com/albums/v4...n/untitled.jpg
And then from there, I had no idea where to go... there hawsehole being 1 fathom above the water really gets to me, perhaps making the above drawing void. Another thing I don't understand is that it says it's anchored in 11 fathoms of water.. how could the question be asking what speed the boat would be moving if it were at 13 fathoms?
2. A ladder 41 feet long was leaning against a vertical wall and begins to slip. Its top slides down the wall whilte its bottom moves along the level ground at a constant speed of 4ft/sec. How fast is the top of the ladder moving when it is 9 feet above the ground?
For this one.. I didn't even know what to do.. of course I drew a triangle, hypotenuse of 41 and the vertical side of 9 feet.. and then.......?
Mainly, I think problems such as these are really easy, but I have a really hard time picturing the problem or drawing it out. I don't know which numbers apply to dx/dt and dy/dt..
|May20-06, 05:48 PM||#2|
And tehy are asking what is the speed when there is 13 fathoms of *chain* still out, which is the length of the hypothenuse on your triangle. Of course this length will be larger or equal to 12 fathoms (it will be equal to 12 fathom when the boat will be right above the anchor)
If we call "L" the length of the hypothenuse, then what you want is to write dx/dt in terms of dL/dt (which is the number they give you). All you have to do is to write an expression relating x and L (and other known values), isolate x in terms of those constants and L, and differentiate both dised with respect to t. You will get dx/dt = expression in terms of constant, L and dL/dt.
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