Experiment: You *are* powerful!

Did this experiment with the children, after I completed (and they assimilated, hopefully) the prerequisites. It was fun.  We climbed up and down the stairs of the over head water  tank – located at some 11 meters from the ground level.

We plan to have a couple of hours of discussion dealing with the subject, (with the children) and will post the details / feedback later.

The following text gives the ‘template’ for doing the experiment.

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Prerequisites: Basic knowledge of what power, work and force mean.

Suggested Target group age band: Elementary – or as soon as children know how power and work are related – energy is the capacity to do work, that is.

Since, how to conduct and record properly formed / controlled experiments has been taught to Erdkinder, it is apt for them too.

Goal(s):

  1. Understanding the units of work (Joules), force (Newtons), energy (Watts)
  2. To know how they are related
  3. What are potential and kinetic energies
  4. To explore whether there are other kinds of energies

Ingredients/Apparatus required: A stop clock (a wrist watch would do too); measuring tape/ruler; weighing machine; a few flights of stairs; children whose energies need to be taken out; the usual notebook and pencil.

Experimental procedure: Time how long it takes a child to walk up a set of flights of stairs; measure the height from the bottom to the top of the flights, If needed, measure the height of one step and multiply it by the number of steps.

Take the mass (not weight!) of the child (measure it with the weighing machine; wonder why it is called the weighing machine, though!).

Computation:

Take the weight of the child in Newtons (mass (= in kgs) X g (= acceleration due to gravity – circa 9.81 meters x second-2 – for easy computation, you can use 10 meters x second-2)) and multiply the total height scaled. This would give the gain of potential energy by the child when he/she goes up.

The work done is in Joules – which is actually kgs X meters X second-2 X meters

Now divide this gain in potential energy by time taken (in seconds) to give the child’s power in Watts.

All children can do this computation. If there are issues of physical inabilities/disabilities, then the adult would have this child do the compute/time etc.

Suggestions:

The children can take turns and measure their power – while one climbs up, the other can time it, etc.

It would be ideal if there are many flights of stairs, but if not one can try climbing the railings of over head tank or if this not available, may be one can even walk.

  • Driving home: Work done = force x distance moved in the direction of the force
  • Driving home: Energy is the capacity to do work
  • Driving home: Power is the energy transferred in a given time; or the capability to do energy transfer in a give time.

Effect: The linking of the text-bookish understanding of force, power and work to something concrete that all of us do on a daily basis. And, the fact that we can measure our power output in a fun way. Thusly, the power of wow!.

Questions for discussion: All thru the presentation, questions from children need to be positively encouraged; to elicit the opinions of children the following types of questions can be posed:

  1. What is your weight in Newtons? (mass in kgs x ‘accleration due to gravity’ in meters/second2)
  2. What would be your weight on say, Moon.
  3. Why can’t I measure the time of my coming down the stairs. (actually you can do that; the thing is there would be a decrease in potential energy and the force of the earth (gravitation) would help you unlike while going up)
  4. What happens when – I carry on my back someone else and walk up? Would he/she have done some work too? Is there a difference in energy of both? What about the power of the person carried?
  5. What could happen if there were no gravity? What would be the difference if we were doing the experiment on the moon?
  6. If the children run up the stairs as opposed to walking up, does it make a difference to their power? (can it be linked to the formula)
  7. If they carry an additional weight, would it make a difference to the power or the work done? To know this does something need to remain constant?
  8. Is there a connection between the power of the individuals and say incandescent bulb wattage ratings such as 100W or 60W or something? Do they actually measure the same? Are we talking about similar things here?
  9. In the same vein, is there any connection to the power output of the vehicles?
  10. If we use or expend/exert similar energy/power while riding bicycles as with walking or climbing, how come we go much faster for the same power output?

Eventually the children should be able to zero-in on the principles behind the effect on their own, but if not, they can be given clues and similar effects.

Closure: There should be definite closure to the demo – repeating and reaffirming the basic principle involved; can take the form of ‘Look, this is what I did and this is what happened. Do we agree that this could be a reason? What do you think happened? Was it <any of the (off tangent) suggestions from the children> or <any of the correct explanations>.’

This will close the activity at the class / environment.

Records / notes: These should be created by the adults for each instance of the experiment – typically as appendices to the same document so that ‘lessons learnt’ could be captured and disseminated later on. This could be some interesting diversions or some interesting questions etc etc.

Precautions: Safety first – the adult has to do the climbing at least once (to see if the stairs or slippery or corroded or whatever danger that could lurk in there) and if the railings are not safe, then walking on the road can be resorted to instead.

Children should not be allowed to crowd around the railing area. No need for any cheerleading or catcalls as this is a ‘scientific’ experiment.

Suggested activities: The children, as a way of reinforcing their learning, should do these; these typically could take the form of the following:

  1. Encouraging them to perform the experiment at home – for the benefit of parents. (may be)
  2. Conducting a quiz on the factoids (oral / written) the following day.
  3. Extensions that the children can be prompted to explore. Are kinetic and potential energies related?
  4. Can the child ‘increase’ its power output – if so how (stamina is the other word for power in the human context and so regular training would help – coupez la difficulte en quatre)
  5. Assuming that the kids do the timing/climbing everyday – can the children draw a graph showing how their power is increasing over a period of time?

Sources:

  1. My impromptu experiments with a few adolescent children many years back. I think any self respecting physics book would cover this kind of experiments and therefore there is nothing major or new here at all.
  2. There could be quite a few websites dealing with the stuff. In any case, NO claims to originality are being made here. And we don’t claim any copyright either!
  3. The purpose of putting up this stuff is to enable others use the method or the madness, if they so desire.
  4. Please refer to the earlier post – these experiments can be done at home too!

Please feel free to comment on the content and style. Suggestions for improvement of the procedure  or feedback after using the idea are welcome.

🙂

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