Homework 12 - vu (tv2894) – Homework 12 (Section 3.8) –...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: vu (tv2894) – Homework 12 (Section 3.8) – miner – (55096) 1 This print-out should have 7 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A rock is thrown into a still pond and causes a circular ripple. If the radius of the ripple is increasing at a rate of 4 ft/sec, at what speed is the area of the ripple increasing when its radius is 6 feet? 1. speed = 48 π sq. ft/sec correct 2. speed = 49 sq. ft/sec 3. speed = 46 π sq. ft/sec 4. speed = 48 sq. ft/sec 5. speed = 47 π sq. ft/sec 6. speed = 47 sq. ft/sec 7. speed = 45 sq. ft/sec 8. speed = 45 π sq. ft/sec Explanation: The area, A , of a circle having radius r is given by A = πr 2 . Differentiating implicitly with respect to t we thus see that dA dt = 2 πr dr dt . When r = 6 , dr dt = 4 , therefore, the speed at which the area of the ripple is increasing is given by speed = 48 π sq. ft/sec . 002 10.0 points A point is moving on the graph of xy = 3. When the point is at (4 , 3 4 ), its x-coordinate is increasing at a rate of 1 units per second. What is the speed of the y-coordinate at that moment and in which direction is it mov- ing? 1. speed = 35 16 units/sec, increasing y 2. speed = 19 16 units/sec, increasing y 3. speed = − 35 16 units/sec, increasing y 4. speed = − 19 16 units/sec, decreasing y 5. speed = − 3 16 units/sec, decreasing y 6. speed = 3 16 units/sec, decreasing y correct Explanation: Provided x, y negationslash = 0, the equation xy = 3 can be written as...
View Full Document

This note was uploaded on 11/07/2010 for the course M 408N taught by Professor Gualdini during the Fall '10 term at University of Texas.

Page1 / 4

Homework 12 - vu (tv2894) – Homework 12 (Section 3.8) –...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online