Day 15: A Standard Unit for Energy


After yesterday's experiments, I decided we should have decided upon a standard unit for energy. In this case, a standard rubberband pulled back some distance stores 1 unit of energy. Need to test how much energy a cart has? Send it into a rubber and see how far it stretches.

I know this isn't perfect, but we aren't developing quantitative relationships now. Just trying to get at the factors which affect the amount of energy in moving carts and stretched rubberbands.

(A puck launcher is pictured here because I forgot to take a picture of my actual set up: two large colored rubberbands from Staples are looped together and stretched across the width of the lab table, secured with c-clamps. A puck launcher would make a nice portable energy measurer. )


About Frank Noschese

HS Physics Teacher constantly questioning my teaching.

One response to “Day 15: A Standard Unit for Energy”

  1. Anonymous says :

    We’re going to start a "Unit 0" energy treatment pretty soon, and I was just thinking today about how to do "quantitative" energy experiments without actually working with the Ek, Egrav, or Eelas relationships (they’re not a priority for the course, at least not at this point, since we haven’t defined ANY of the things that make up those relationships!). It seemed like we could make some solid conclusions using only length measurements: for height, rubber band stretching, and maybe even "sliding distance." We could, for example, determine that Eelas doesn’t depend on how much mass is doing the stretching, but Egrav definitely depends on how much mass is being raised.So, I REALLY like the idea of defining a local "unit" of energy, but is it a problem that it doesn’t go linearly with x? I was thinking that this could be another awesome relationship (effect of drop height for a cart on rubber band displacement, AND vice versa), but this squared relationship is going to be a little gnarly for many of my ninth graders… I wonder if we should just use a quantified "number of rubber bands" instead.

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