Which could be the best examples to explain Inertial Reference Frame in the High School?
The best way to begin with, is to tell people what is a non-inertial frame. For illustrating this, one can place a piece of chalk on a gyroscope, then make the gyroscope to rotate. The chalk would fly off the gyroscope surface, although no force acts on it.
The chalk tends to maintain its state at rest with respect to the lab, but with respect to the gyroscope surface it has a velocity that changes direction - wherefrom there appears an acceleration with respect to the gyroscope, as if a force acts on the chalk.
This is a so-called pseudo-force, i.e. a force that appears without the action of another body or field on the chalk. Coordinate frames in which act such forces are named non-inertial, because a body left free, not attached tightly to the frame, doesn't preserve its state of motion - state of rest in our case.
To the difference, a frame in which a free body preserves its state of movement in absence of action of bodies or fields, i.e. there are no pseudo-forces, is named an inertial frame.
Hi.
Teach physics to High School students is a considerable challenge. Since I'm also a Computer Graphics teacher, I frequently develop animations and simulations with PoV-Ray and Blender (free CG software). If you are comfortable to write some programs, you can also try WebGL and Three.js. A (possible) easier way is to use "Modellus" to build some simulations (link: http://modellus.co/index.php/pt/).
Um abraço,
Tarcisio.
Thank you Tarcisio. I will follow your recommendation and try programming some examples. Sometimes the best idea is to develop the examples ourselves.
The best way to begin with, is to tell people what is a non-inertial frame. For illustrating this, one can place a piece of chalk on a gyroscope, then make the gyroscope to rotate. The chalk would fly off the gyroscope surface, although no force acts on it.
The chalk tends to maintain its state at rest with respect to the lab, but with respect to the gyroscope surface it has a velocity that changes direction - wherefrom there appears an acceleration with respect to the gyroscope, as if a force acts on the chalk.
This is a so-called pseudo-force, i.e. a force that appears without the action of another body or field on the chalk. Coordinate frames in which act such forces are named non-inertial, because a body left free, not attached tightly to the frame, doesn't preserve its state of motion - state of rest in our case.
To the difference, a frame in which a free body preserves its state of movement in absence of action of bodies or fields, i.e. there are no pseudo-forces, is named an inertial frame.
Hi, Jair.
Just another idea. Before you start creating programs, simulations and/or animations, consider the previous conceptions of the students. Survey them. Information that come from their empirical knowledge / common sense may help you to build better learning objects.
Um abraço,
Tarcisio.
Thank you Sofia! The combination of live experiments and computer animations will make it work. I tried already with some small objects available in the classroom and I succeeded somehow. The biggest challenge comes with rigid bodies in rotation. The students can not find an appropriate reference frame to affirm that rotation is a kind of movement. They have the idea of translation that only if the distance between the reference frame and the object keeps changing, we have movement.
You might want to look at my paper (you can download it from researchgate
Conference Paper: Toward a Hermeneutic-Historical Approach in Resolving Dilemmas in Teaching: Newton’s First Law as an Exemplar
Gyoungho Lee · Roland M. Schulz · Calvin S. Kalman · Richardo L. Coelho
12th Biennial International History and Philosophy of Science Teaching Group Conference, Pittsburgh; 06/2013
For the related fact that force is related to acceleration (not velocity) I have found it useful to make the following observation: consider all familiar instances in which motion appears uniform, or even rest. Most of the time you can identify two forces at equilibrium. Examples: carrying a pail of water, driving a car at constant velocity (motor and friction), pushing or dragging a box etc.. Now imagine any case where such equilibria are suddenly broken (dropping the pail, cutting the motor, stopping to push on the box, or, on the contrary, having the box suddenly pass to a surface with much less friction). In all these cases, changes of velocity are clearly seen. So that may suggest that forces in general are in the business of causing acceleration, whereas to maintain velocity, you need two forces in equilibrium, which, one may then point out, mount to zero force.
In my opinion it is virtually hopeless to appeal to ``frictionless'' situations, as these simply do not appear in everyday life.
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