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Expert: Alon Mandes - 4/3/2009


Question
a potter places a cylindrical lump of clay on her wheel.  before she begins to shape it the radius=10 and height=4.  how fast is the height changing when radius=7.5, given that the radius is shrinking by 6/5 in/min

Answer
During the shaping process , the surface area (the amount of lump)
doesn't change. That means, at every moment t : 2πr(t)h(t)=So .
Where So=2π*10*4=80π the initial amount of surface area of lump.
So, now we can find a relation between r & h : r(t)h(t)=80π/2π=40 .
Thus, r(t)=40/h(t). Let's derive :
r'(t)=-40h'(t)/h(t)²
-6/5 =-40h'(t)/7.5²
-6/5 =-40h'(t)/56.25
h'(t)=1.6875 in/min

Alon.

Calculus

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Alon Mandes

Expertise

Kind of questions I can answer : Limits, Derivatives, Integration, Implicit functions, continuousity, differentiation ,Extremum problems, Lagrange multipliers, Gradients, Surface integrals, Multi variables functions ,Multi variables Integrals,Complex variables ,Complex functions, Curves, Trajectory integrals & Vector analyse,Divergence,Rotor & word problems. Kind of question I can't answer : Economics,Combinatorics,infinite series & convergence ,Statistics & Probabilities .

Experience

1. I'm a team member of mathnerds (math site for answering questions) 2. I'm a team member in the Student's Union of the Technion, helping students who have problems in mathematics. 3. 2 years of experience as a math teacher in college. 4. I give free homework help for high school students in Mathematics & Physics. 5. I teach part time in collage the subjects : "Digital Signal Processing" , "Random Signals & Noise" , "Complex Functions".

Organizations
Hi-Tech company : GSM4VOIP ; job possition : Algorythm developer.

Education/Credentials
M.A in Mathematics & Bs.c in Electronics.

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