Word Problem Involving Velocities, Acceleration, Limits












1












$begingroup$


This is the problem:





I took the integral of a(t) to get v(t) and got $v(t)$ = $ln(t+2)$ $-$ $ln(t+3)$ + C . I plugged in the initial conditions and got C = 0. Then when I took the limit, I know it's a telescoping series so everything cancels out except the $ln(2)$ but that's not an answer choice so I'm confused what I did wrong.










share|cite|improve this question











$endgroup$

















    1












    $begingroup$


    This is the problem:





    I took the integral of a(t) to get v(t) and got $v(t)$ = $ln(t+2)$ $-$ $ln(t+3)$ + C . I plugged in the initial conditions and got C = 0. Then when I took the limit, I know it's a telescoping series so everything cancels out except the $ln(2)$ but that's not an answer choice so I'm confused what I did wrong.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      This is the problem:





      I took the integral of a(t) to get v(t) and got $v(t)$ = $ln(t+2)$ $-$ $ln(t+3)$ + C . I plugged in the initial conditions and got C = 0. Then when I took the limit, I know it's a telescoping series so everything cancels out except the $ln(2)$ but that's not an answer choice so I'm confused what I did wrong.










      share|cite|improve this question











      $endgroup$




      This is the problem:





      I took the integral of a(t) to get v(t) and got $v(t)$ = $ln(t+2)$ $-$ $ln(t+3)$ + C . I plugged in the initial conditions and got C = 0. Then when I took the limit, I know it's a telescoping series so everything cancels out except the $ln(2)$ but that's not an answer choice so I'm confused what I did wrong.







      calculus integration






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Dec 19 '18 at 4:44









      Andrei

      12.4k21128




      12.4k21128










      asked Dec 19 '18 at 4:40









      krauser126krauser126

      474




      474






















          2 Answers
          2






          active

          oldest

          votes


















          1












          $begingroup$

          Here I assume that the initial velocity refers to $v(0) = ln frac{2}{3}$:
          $$v(t) = ln frac{t+2}{t+3} = ln frac{1+frac{2}{t}}{1+frac{3}{t}}stackrel{t to infty}{longrightarrow}ln 1 = 0$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:53










          • $begingroup$
            @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:07










          • $begingroup$
            [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
            $endgroup$
            – krauser126
            Dec 19 '18 at 5:15










          • $begingroup$
            @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:26










          • $begingroup$
            @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:34





















          0












          $begingroup$

          You have
          $$
          v(t)=lntfrac23+int_0^tfrac1{u^2+5u+6},du=lntfrac23+lnfrac{t+2}{t+3}+lntfrac32,
          $$

          where the $ln tfrac32$ comes from evaluating the antiderivative at $0$. Then
          $$
          lim_{ttoinfty}v(t)=ln tfrac23+ln tfrac32=0.
          $$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:52










          • $begingroup$
            Now I see that I misread something. Give me a second.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:56










          • $begingroup$
            You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:59











          Your Answer





          StackExchange.ifUsing("editor", function () {
          return StackExchange.using("mathjaxEditing", function () {
          StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
          StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
          });
          });
          }, "mathjax-editing");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "69"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          noCode: true, onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3046002%2fword-problem-involving-velocities-acceleration-limits%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          Here I assume that the initial velocity refers to $v(0) = ln frac{2}{3}$:
          $$v(t) = ln frac{t+2}{t+3} = ln frac{1+frac{2}{t}}{1+frac{3}{t}}stackrel{t to infty}{longrightarrow}ln 1 = 0$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:53










          • $begingroup$
            @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:07










          • $begingroup$
            [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
            $endgroup$
            – krauser126
            Dec 19 '18 at 5:15










          • $begingroup$
            @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:26










          • $begingroup$
            @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:34


















          1












          $begingroup$

          Here I assume that the initial velocity refers to $v(0) = ln frac{2}{3}$:
          $$v(t) = ln frac{t+2}{t+3} = ln frac{1+frac{2}{t}}{1+frac{3}{t}}stackrel{t to infty}{longrightarrow}ln 1 = 0$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:53










          • $begingroup$
            @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:07










          • $begingroup$
            [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
            $endgroup$
            – krauser126
            Dec 19 '18 at 5:15










          • $begingroup$
            @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:26










          • $begingroup$
            @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:34
















          1












          1








          1





          $begingroup$

          Here I assume that the initial velocity refers to $v(0) = ln frac{2}{3}$:
          $$v(t) = ln frac{t+2}{t+3} = ln frac{1+frac{2}{t}}{1+frac{3}{t}}stackrel{t to infty}{longrightarrow}ln 1 = 0$$






          share|cite|improve this answer











          $endgroup$



          Here I assume that the initial velocity refers to $v(0) = ln frac{2}{3}$:
          $$v(t) = ln frac{t+2}{t+3} = ln frac{1+frac{2}{t}}{1+frac{3}{t}}stackrel{t to infty}{longrightarrow}ln 1 = 0$$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 19 '18 at 4:58

























          answered Dec 19 '18 at 4:47









          trancelocationtrancelocation

          12.3k1826




          12.3k1826












          • $begingroup$
            That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:53










          • $begingroup$
            @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:07










          • $begingroup$
            [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
            $endgroup$
            – krauser126
            Dec 19 '18 at 5:15










          • $begingroup$
            @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:26










          • $begingroup$
            @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:34




















          • $begingroup$
            That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:53










          • $begingroup$
            @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:07










          • $begingroup$
            [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
            $endgroup$
            – krauser126
            Dec 19 '18 at 5:15










          • $begingroup$
            @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:26










          • $begingroup$
            @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
            $endgroup$
            – trancelocation
            Dec 19 '18 at 5:34


















          $begingroup$
          That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
          $endgroup$
          – krauser126
          Dec 19 '18 at 4:53




          $begingroup$
          That makes sense. However, why doesn't using the fact that they're telescopic work in this case?
          $endgroup$
          – krauser126
          Dec 19 '18 at 4:53












          $begingroup$
          @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
          $endgroup$
          – trancelocation
          Dec 19 '18 at 5:07




          $begingroup$
          @krauser126 Could you please write down the telescoping sum you are referring to? This might clear up what went wrong.
          $endgroup$
          – trancelocation
          Dec 19 '18 at 5:07












          $begingroup$
          [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
          $endgroup$
          – krauser126
          Dec 19 '18 at 5:15




          $begingroup$
          [ln (2) + ln(3) + ln(4) + ...] - [ln (3) + ln (4) + ln (5) + ...] Since its from t = 0 to t = infinity. So wouldnt all the terms in the negative set cancel with those equivalent in the positive set, leaving + ln(2) as the first term left over.
          $endgroup$
          – krauser126
          Dec 19 '18 at 5:15












          $begingroup$
          @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
          $endgroup$
          – trancelocation
          Dec 19 '18 at 5:26




          $begingroup$
          @krauser126 This expression would be adding the velocities at specific points: $v(0) + v(1) + cdots $ and does not represent the limit for $t to infty$
          $endgroup$
          – trancelocation
          Dec 19 '18 at 5:26












          $begingroup$
          @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
          $endgroup$
          – trancelocation
          Dec 19 '18 at 5:34






          $begingroup$
          @krauser126 Besides this: what you wrote is an undefined expression: $infty - infty$. If you set $v(k) = ln (k+2) - ln (k+3)$ you would get $$Rightarrow sum_{k=0}^n v(k) = sum_{k=0}^n (ln (k+2) - ln (k+3)) = ln 2 - ln (n+3)$$ Now ask yourself whether this reflects the question to be answered.
          $endgroup$
          – trancelocation
          Dec 19 '18 at 5:34













          0












          $begingroup$

          You have
          $$
          v(t)=lntfrac23+int_0^tfrac1{u^2+5u+6},du=lntfrac23+lnfrac{t+2}{t+3}+lntfrac32,
          $$

          where the $ln tfrac32$ comes from evaluating the antiderivative at $0$. Then
          $$
          lim_{ttoinfty}v(t)=ln tfrac23+ln tfrac32=0.
          $$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:52










          • $begingroup$
            Now I see that I misread something. Give me a second.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:56










          • $begingroup$
            You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:59
















          0












          $begingroup$

          You have
          $$
          v(t)=lntfrac23+int_0^tfrac1{u^2+5u+6},du=lntfrac23+lnfrac{t+2}{t+3}+lntfrac32,
          $$

          where the $ln tfrac32$ comes from evaluating the antiderivative at $0$. Then
          $$
          lim_{ttoinfty}v(t)=ln tfrac23+ln tfrac32=0.
          $$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:52










          • $begingroup$
            Now I see that I misread something. Give me a second.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:56










          • $begingroup$
            You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:59














          0












          0








          0





          $begingroup$

          You have
          $$
          v(t)=lntfrac23+int_0^tfrac1{u^2+5u+6},du=lntfrac23+lnfrac{t+2}{t+3}+lntfrac32,
          $$

          where the $ln tfrac32$ comes from evaluating the antiderivative at $0$. Then
          $$
          lim_{ttoinfty}v(t)=ln tfrac23+ln tfrac32=0.
          $$






          share|cite|improve this answer











          $endgroup$



          You have
          $$
          v(t)=lntfrac23+int_0^tfrac1{u^2+5u+6},du=lntfrac23+lnfrac{t+2}{t+3}+lntfrac32,
          $$

          where the $ln tfrac32$ comes from evaluating the antiderivative at $0$. Then
          $$
          lim_{ttoinfty}v(t)=ln tfrac23+ln tfrac32=0.
          $$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 19 '18 at 4:58

























          answered Dec 19 '18 at 4:49









          Martin ArgeramiMartin Argerami

          127k1182183




          127k1182183












          • $begingroup$
            I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:52










          • $begingroup$
            Now I see that I misread something. Give me a second.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:56










          • $begingroup$
            You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:59


















          • $begingroup$
            I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
            $endgroup$
            – krauser126
            Dec 19 '18 at 4:52










          • $begingroup$
            Now I see that I misread something. Give me a second.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:56










          • $begingroup$
            You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
            $endgroup$
            – Martin Argerami
            Dec 19 '18 at 4:59
















          $begingroup$
          I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
          $endgroup$
          – krauser126
          Dec 19 '18 at 4:52




          $begingroup$
          I didn't understand a thing you did. Doesn't it tell us that the velocity is initially ln(2/3) so that we can use that as an initial condition to plug t = 0 and solve for C, which I did already and got C = 0. So why did you do that additional step.
          $endgroup$
          – krauser126
          Dec 19 '18 at 4:52












          $begingroup$
          Now I see that I misread something. Give me a second.
          $endgroup$
          – Martin Argerami
          Dec 19 '18 at 4:56




          $begingroup$
          Now I see that I misread something. Give me a second.
          $endgroup$
          – Martin Argerami
          Dec 19 '18 at 4:56












          $begingroup$
          You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
          $endgroup$
          – Martin Argerami
          Dec 19 '18 at 4:59




          $begingroup$
          You can do it as I did, or you find that $C=0$. In any case, the limit is zero.
          $endgroup$
          – Martin Argerami
          Dec 19 '18 at 4:59


















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Mathematics Stack Exchange!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          Use MathJax to format equations. MathJax reference.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3046002%2fword-problem-involving-velocities-acceleration-limits%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          Popular posts from this blog

          Tonle Sap (See)

          I get strange results when I access the Sqlitedatabase with Unity C# via XAMPP

          Guatemaltekische Davis-Cup-Mannschaft