Skip to main content
Physics LibreTexts

14.3: Unit 9 Lab Extension Part I- Replenishing Energy*

  • Page ID
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    Jump Analysis Continued…

    You will need to refer to the data and analysis from the Unit 9 Lab throughout this activity.

    Human Performance

    What is the change in kinetic energy of the person during the launch phase of the jump, from stationary to leaving the force plate?

    What is the net work done on the person during the launch phase? (Work-Energy Theorem)

    Use your video to find the distance the person’s center of mass moved during the launch phase. Record here:

    Using the distance above and the net work from the start of this section, find the average net force during the launch phase. (Work Equation)

    What average force needs to be supplied by your Achilles tendon in order to have the average net force you found above. (This force needs to be large enough to cancel your weight, AND still have the net force you found above left over!)

    Use this force and the launch distance you found to determine the work done by the jumper.

    Where did the energy to do this work come from?

    You have to supply basically the same work to stop your motion on landing than you provided to stop it on launch. How much energy must you supply for one jump?

    If a person performed one of these jumps per second for a whole day, how many Joules of work would they do?

    Assuming a 20% mechanical efficiency, how much energy do you actually expend to do this work? (You have to do 5x more work than actual mechanical energy you get out).

    How many extra food calories is that?

    You also need about 2000 Calories per day for basic metabolism, so how many 260 Calorie candy bars would you need to eat in order to maintain calorie balance?

    If you did not eat any candy bars how many pounds of fat would you need to metabolize to provide this energy? Cite any sources for the calories per pound of fat metabolized.

    This page titled 14.3: Unit 9 Lab Extension Part I- Replenishing Energy* is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Lawrence Davis (OpenOregon) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.