Physics of playthings: Pump rocket
The third day of the physics of playthings intended to look at the number of pumps versus height for a couple of pump rockets.
I mistakenly thought that like the water rockets oa smallf my youth, one pumped a chamber and then released the rocket. I intentionally had not opened the packages so the students would know that I did not know what the rockets would do. This makes the exploration feel more real, and is certainly makes the activity unpredictable for me.
Upon opening I discovered that the rockets do not work that way. You simple pump once, the harder or farther one pumps, the higher the rocket goes. Only at the end of the period did I discover a small hole in the handle that should be covered to maximize the amount of air pushing the rocket. That hole is an intake when the pump handle is extended. Leaving it open bleeds air on the pump action and decreases the air pressure launching the foam rocket.
Before we went outside I outlined the data gathering. I knew we would be doing this rather roughly. I did not want to use the plumb bob on the protractor approach because I know that adds in a 90° minus the angle on the protractor complication. This was going to be very rough and ready measurements.
The basic layout can be seen here. I am 500 cm from the launch point with a yard stick and a protractor. I am holding the protractor level by guess and golly. I attempt to site the maximum height and then check the angle. The class has no background with angular measurements in the lab, and the calculation will involved the tangent function, which only a few have seen before.
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