The physics of the everyday

Saroja Sreekanth

Denis Rancourt, a renowned professor of physics is known for his radical views on the approach to pedagogy. He once wrote: “No one learns physics from being taught physics. The best way to teach physics is not to teach physics.”

Most students today have little opportunity to thoroughly understand physical laws and principles based on their own observations and inferences. Physics textbooks outline the laws and rules and quickly get into numerical problem solving, so students are deprived of a hands-on approach to science learning. This impedes them from discovering and internalizing the concept for themselves in the most lasting and fun way. Isn’t textbook based teaching indirectly responsible for making learning a difficult and sometimes unpalatable experience for students? Often, it drives them to an inevitable dependence on memorization and inaccurate abstract thought.

A true understanding of underlying concepts and the ability to use the knowledge so gained in a new situation best happens with cause-and-effect thinking. Ideally, students should begin to question, realize, and ultimately appreciate the ‘physics’ in action constantly all around them. As teachers, we should endeavor to connect the topics in physics provided by the text to students’ experiences by helping them to ‘see’ the meaning of the scientific terms and principles in their book.

Motivating students to learn using simple activities and demonstrations helps to engage students actively and thoughtfully. While keeping up with course work, it also establishes better student-teacher interaction and a productive class. I share with you my experiences in teaching two topics in Mechanics, which could be otherwise construed as abstract and uninteresting. Most topics in elementary physics can be covered in this way.

Center of gravity and stability
These simple ‘dares’ direct attention to the fact that they are extremely challenging to perform due to the position of your Center of Gravity (CG).

• Sit on a chair, feet flat on the ground, arms crossed on the chest and back upright. Try to stand up, without bending forward even a little.
• Stand with back and heels touching a wall, feet stiff, and keep your arms by your side. Without lunging forward even a bit, try to jump. How about stepping forward?

Encourage the students to attempt the tasks several times. A followup discussion of ‘why or why not’ something worked or didn’t helps understand the ‘centre of gravity’ concept in relation to the supporting base, and the conditions necessary for stability and
for movement. Draw attention to the fact that the human body learns to maintain balance by making small adjustments like bending forward to shift the CG away from the support base to enable motion (movement). We don’t need to think about it because it becomes an automatic reflex. An interesting example of how the CG can be rapidly moved around artfully to maintain balance is the skier. This can be clarified through a slow motion video of a person skiing showing their body movements and the quick change in direction. To wind up the unit, demonstrate balancing toys and arrangements.

Atmospheric pressure
The ocean of air we live in exerts tremendous pressure in all directions. We don’t feel it. How then do we believe it to be true?

• Take two identical sized plumber’s plungers. Wet the rims of the rubber ends and push them tightly together. Once stuck, have two students hold the handles and wage a tug-of-war. Who wins? The same principle lies behind suction darts thrown on to a board, or a lizard walking up vertical walls.
• Can you lift magazines up with your breath? Place a strong paper (or thick plastic) bag on a flat surface, pile a few magazines over the bag, and blow hard after tightly squeezing together the opening of the bag.
• Spread a sheet of newspaper on a table top, insert a ruler under the paper, so half of it sticks out over the edge. Smooth the paper out, then strike the ruler with a quick blow. Now gently press the ruler down. Observe and explain the difference.

A follow-up discussion should help understand why living beings on earth are not crushed by air pressure, the use of tyres, and similar instances of air pressure at work to assist us.

Fluid pressure in motion
Changing a pocket of air pressure makes for movement. Airplanes fly, and gusts of wind and tornadoes occur by using this principle of physics. Here are a few activities using balls, straws, and a funnel to see this happen in front of your eyes:

• Hold a funnel up, place a small plastic ball in it, and with a steady blow try to push the ball out of the funnel.
• Hold a lighted candle at a safe distance, and use the funnel to blow out the flame.
• Cut a strip of thin paper, say 3cm x 11cm, hold it close to your mouth and blow down on the paper to watch the effect.
• Take two drinking straws and a glass of water. Put both straws in your mouth with the free end of one straw in the water and the other outside the glass. Try drinking the water.

No study of fluid pressure would be complete without the mention of ‘streamlining’ in the design of all fast moving vehicles – cars on land, aeroplanes or rockets in air, and submarines and ships in water. Shaping not only of the front but also the back helps in lowering air or water resistance, thus increasing speed and ease of movement. Swimmers and divers will be able to appreciate this point.

By connecting the treatment of physics outlined in the textbook to students’ daily experiences using easy and quick activities will help rid them of science anxiety and avoidance. It helps stimulate those who are not academically thriving or who have not shown interest in the subject and awakens their natural talents and thinking. A 5th grade teacher once said: “If students are having fun doing and learning, then as a teacher I am having fun at my job, and am a happier person overall!”

The author has taught math and physics for middle and high school classes. She can be reached at saroja@gmail.com.