Thread: Related Rate Again..

1. Let be the area of a circle with radius . If , find when .

2. The radius of a right circular cone is increasing at a rate of 4 inches per second and its height is decreasing at a rate of 3 inches per second. At what rate is the volume of the cone changing when the radius is 50 inches and the height is 20 inches?

3. At noon, ship A is 20 nautical miles due west of ship B. Ship A is sailing west at 23 knots and ship B is sailing north at 22 knots. How fast (in knots) is the distance between the ships changing at 6 PM? (Note: 1 knot is a speed of 1 nautical mile per hour.)

4. The top of a 28 foot ladder, leaning against a vertical wall, is slipping down the wall at the rate of 4 feet per second. How fast is the bottom of the ladder sliding along the ground when the bottom of the ladder is 7 feet away from the base of the wall?

Lets take a look at #1 and #2

1)

Area of a circle:



Then, by implicit differentiation,



And we know and r = 1, so we can get


2)

Volume of a right circular cone:



Then, again by implicit differentiation,



and this time we know , , r = 50, h = 20

Sorry but just dont do number 4..i got the answer already