Rate of change of cross-section of cylinder












2












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I got this task on my calculus class and I got stuck at process of figuring it out



A clay cylinder is being compressed so that its height is changing at the rate of 4 millimeters per second, and its diameter is increasing at the rate of 2 millimeters per second. Find the rate of change of the area of the horizontal cross-section of the cylinder when its height is 1 centimeter.



What I know:



Volume is unknown and constant



Rate of change of diameter is $$dfrac {dD}{dt} = 0,2text{cm}/text{sec}$$
Rate of change of height is $$dfrac {dh}{dt} = -0,4text{cm}/text{sec}$$
Trying to find $dfrac{dD}{dt}$ by using formula $$V=pi r^2h$$










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    2












    $begingroup$


    I got this task on my calculus class and I got stuck at process of figuring it out



    A clay cylinder is being compressed so that its height is changing at the rate of 4 millimeters per second, and its diameter is increasing at the rate of 2 millimeters per second. Find the rate of change of the area of the horizontal cross-section of the cylinder when its height is 1 centimeter.



    What I know:



    Volume is unknown and constant



    Rate of change of diameter is $$dfrac {dD}{dt} = 0,2text{cm}/text{sec}$$
    Rate of change of height is $$dfrac {dh}{dt} = -0,4text{cm}/text{sec}$$
    Trying to find $dfrac{dD}{dt}$ by using formula $$V=pi r^2h$$










    share|cite|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      I got this task on my calculus class and I got stuck at process of figuring it out



      A clay cylinder is being compressed so that its height is changing at the rate of 4 millimeters per second, and its diameter is increasing at the rate of 2 millimeters per second. Find the rate of change of the area of the horizontal cross-section of the cylinder when its height is 1 centimeter.



      What I know:



      Volume is unknown and constant



      Rate of change of diameter is $$dfrac {dD}{dt} = 0,2text{cm}/text{sec}$$
      Rate of change of height is $$dfrac {dh}{dt} = -0,4text{cm}/text{sec}$$
      Trying to find $dfrac{dD}{dt}$ by using formula $$V=pi r^2h$$










      share|cite|improve this question











      $endgroup$




      I got this task on my calculus class and I got stuck at process of figuring it out



      A clay cylinder is being compressed so that its height is changing at the rate of 4 millimeters per second, and its diameter is increasing at the rate of 2 millimeters per second. Find the rate of change of the area of the horizontal cross-section of the cylinder when its height is 1 centimeter.



      What I know:



      Volume is unknown and constant



      Rate of change of diameter is $$dfrac {dD}{dt} = 0,2text{cm}/text{sec}$$
      Rate of change of height is $$dfrac {dh}{dt} = -0,4text{cm}/text{sec}$$
      Trying to find $dfrac{dD}{dt}$ by using formula $$V=pi r^2h$$







      calculus






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Jan 17 at 9:36







      Evgeniy

















      asked Jan 17 at 9:19









      EvgeniyEvgeniy

      134




      134






















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          $begingroup$

          So, First we know that $$V=frac{pi D^2 h}{4} $$ where $D$ is the Diameter, and $h$ is the height.
          Now by differentiating this with respect to time, we get,



          $frac{dV}{dt} = frac {partial V}{partial D}frac{dD}{dt} + frac {partial V}{partial h}frac{dh}{dt}$



          $;;;;;= frac{pi D h}{2} frac{dD}{dt} + frac{pi D^2}{4} frac{dh}{dt}$



          Now, $frac {dV}{dt} = 0 ; ; frac{dD}{dt}=2; ; frac{dh}{dt} = -4; ;;; and ;;; h=10 $



          (Note: All units are in mm)



          Solving for $D$ we get, $D=10 mm$



          Now coming back to the question we are needed to find $$frac {dA}{dt}$$



          where $A= frac {pi D^2}{4}$ (Cross sectional area)



          Taking derivative with respect to time, we get,
          $frac {dA}{dt} = frac {pi D}{2} frac {dD}{dt}$



          Plugging in values, we obtain,



          $mathbf {frac {dA}{dt} = 10 pi ; ;mm^2/s}$






          share|cite|improve this answer









          $endgroup$













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            1 Answer
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            1 Answer
            1






            active

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            active

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            active

            oldest

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            0












            $begingroup$

            So, First we know that $$V=frac{pi D^2 h}{4} $$ where $D$ is the Diameter, and $h$ is the height.
            Now by differentiating this with respect to time, we get,



            $frac{dV}{dt} = frac {partial V}{partial D}frac{dD}{dt} + frac {partial V}{partial h}frac{dh}{dt}$



            $;;;;;= frac{pi D h}{2} frac{dD}{dt} + frac{pi D^2}{4} frac{dh}{dt}$



            Now, $frac {dV}{dt} = 0 ; ; frac{dD}{dt}=2; ; frac{dh}{dt} = -4; ;;; and ;;; h=10 $



            (Note: All units are in mm)



            Solving for $D$ we get, $D=10 mm$



            Now coming back to the question we are needed to find $$frac {dA}{dt}$$



            where $A= frac {pi D^2}{4}$ (Cross sectional area)



            Taking derivative with respect to time, we get,
            $frac {dA}{dt} = frac {pi D}{2} frac {dD}{dt}$



            Plugging in values, we obtain,



            $mathbf {frac {dA}{dt} = 10 pi ; ;mm^2/s}$






            share|cite|improve this answer









            $endgroup$


















              0












              $begingroup$

              So, First we know that $$V=frac{pi D^2 h}{4} $$ where $D$ is the Diameter, and $h$ is the height.
              Now by differentiating this with respect to time, we get,



              $frac{dV}{dt} = frac {partial V}{partial D}frac{dD}{dt} + frac {partial V}{partial h}frac{dh}{dt}$



              $;;;;;= frac{pi D h}{2} frac{dD}{dt} + frac{pi D^2}{4} frac{dh}{dt}$



              Now, $frac {dV}{dt} = 0 ; ; frac{dD}{dt}=2; ; frac{dh}{dt} = -4; ;;; and ;;; h=10 $



              (Note: All units are in mm)



              Solving for $D$ we get, $D=10 mm$



              Now coming back to the question we are needed to find $$frac {dA}{dt}$$



              where $A= frac {pi D^2}{4}$ (Cross sectional area)



              Taking derivative with respect to time, we get,
              $frac {dA}{dt} = frac {pi D}{2} frac {dD}{dt}$



              Plugging in values, we obtain,



              $mathbf {frac {dA}{dt} = 10 pi ; ;mm^2/s}$






              share|cite|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                So, First we know that $$V=frac{pi D^2 h}{4} $$ where $D$ is the Diameter, and $h$ is the height.
                Now by differentiating this with respect to time, we get,



                $frac{dV}{dt} = frac {partial V}{partial D}frac{dD}{dt} + frac {partial V}{partial h}frac{dh}{dt}$



                $;;;;;= frac{pi D h}{2} frac{dD}{dt} + frac{pi D^2}{4} frac{dh}{dt}$



                Now, $frac {dV}{dt} = 0 ; ; frac{dD}{dt}=2; ; frac{dh}{dt} = -4; ;;; and ;;; h=10 $



                (Note: All units are in mm)



                Solving for $D$ we get, $D=10 mm$



                Now coming back to the question we are needed to find $$frac {dA}{dt}$$



                where $A= frac {pi D^2}{4}$ (Cross sectional area)



                Taking derivative with respect to time, we get,
                $frac {dA}{dt} = frac {pi D}{2} frac {dD}{dt}$



                Plugging in values, we obtain,



                $mathbf {frac {dA}{dt} = 10 pi ; ;mm^2/s}$






                share|cite|improve this answer









                $endgroup$



                So, First we know that $$V=frac{pi D^2 h}{4} $$ where $D$ is the Diameter, and $h$ is the height.
                Now by differentiating this with respect to time, we get,



                $frac{dV}{dt} = frac {partial V}{partial D}frac{dD}{dt} + frac {partial V}{partial h}frac{dh}{dt}$



                $;;;;;= frac{pi D h}{2} frac{dD}{dt} + frac{pi D^2}{4} frac{dh}{dt}$



                Now, $frac {dV}{dt} = 0 ; ; frac{dD}{dt}=2; ; frac{dh}{dt} = -4; ;;; and ;;; h=10 $



                (Note: All units are in mm)



                Solving for $D$ we get, $D=10 mm$



                Now coming back to the question we are needed to find $$frac {dA}{dt}$$



                where $A= frac {pi D^2}{4}$ (Cross sectional area)



                Taking derivative with respect to time, we get,
                $frac {dA}{dt} = frac {pi D}{2} frac {dD}{dt}$



                Plugging in values, we obtain,



                $mathbf {frac {dA}{dt} = 10 pi ; ;mm^2/s}$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 17 at 10:08









                The Jade EmperorThe Jade Emperor

                908




                908






























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