🚀 go-pugleaf

I do not know where to get the equipment for the "hunter and monkey" demo.
But I was inspired by the note posted yesterday and simulated the demo with
the Interactive Physics tool on the screen of my computer. The tool can be
ordered for MAC or IBM; call Knowledge Revolution at (800)-766-6615. Also
see their advertizing in the last issue of The Physics Teacher.
Here is what I did.

1. A small circle A was placed in the lower left corner (x=0, y=0), the initial
   location of my roung projectile. A small rectangle, B, was placed in the
   upper right corner (x=6.5 y=3.5, in meters displayed along the rulers), the
   initial position of the monkey.

2. The angle T between the line AB and the horizontal was calculated from the
   coordinates (T=28.3 degrees) but you can ask students to measure it with a
   protractor after plotting the diagram on the graph paper. To aim at the
   monkey means to assign the initial velocity to the dart as:

   Vx=Vo*cos(T) and Vy=Vo*sin(T), where Vo is an arbitrary initial speed.

   On the small screen of my MAC/SE30 the values of Vo=8 m/s resulted in the
   hit slightly above the "ground level". The hit is significantly higher when
   Vo is doubled. I used the accuracy of 0.01 seconds per step. A higher
   accuracy, for example 0.001 s/step, slows down simulations to nearly one
   minute (real time is less than one second).

3. I ran the simulation with several Vo between 5 and 15 m/s and watched the
   monkey being hit at different times and different elevations. Watching what
   happens after collisions was also very instructive; Just for fun I started
   assigning different masses (and different elasticities) to colliding objects.

You may challenge students by asking about the effect of gravity (there is a
command for changing g) and about the effect of air resistance (there is a
command for this too). You can place the timer on the screen and assign
speedometers to moving objects. And, unlike in real world, you can turn
gravity off. Interactive Physics is fun, but do not forget that it shows
realistic simulations rather then reality itself. There is some disagreement
among educators about the role of simulations in teaching physics. What do
you think about simulations? How should simulated experiments be used? What
are the pitfalls to avoid in collecting data from simulated reality?

               Ludwik Kowalski     Kowalski@apollo.montclair.edu