A “Fun Physics” workshop for high school pupils
 

Paper published in Spectrum (South Africa) 34:4 (1996) 54-55
 

Download the activity sheet here
 

Introduction.

Over the last few years we have developed a hands-on  “Fun Physics” workshop for use with groups of high school pupils.  The overriding principle when putting together these activities was to demonstrate the nature of the scientific enterprise through the process of prediction, experimentation, observation and explanation.  The pupils are able to do all the activities themselves and, furthermore,  the materials used in the various activities are commonplace and cheap and allow for the activities to be tried again at home.

We have found that the activities work best with standard eight and nine pupils, but have used them successfully with standard sevens and even matrics.  The sessions have lasted from anywhere between one and three hours and the activities are chosen according to the time available and the level of the class.  The class is first divided up into smaller groups of between seven and ten pupils.  Each of these groups is facilitated by an instructor who guides the discussion.  A set of worksheets is given to each pupil describing the various activities and each group is provided with a set of the appropriate apparatus.  All the worksheets follow a similar format: an example of one of these worksheets is shown in figure 1.  The activity is first described and the pupils are asked to make a prediction in the space provided.  At this point the group members usually argue about the possible outcomes of the activity and facilitator can call for a vote.  The pupils then do the activity, the results of which can also be recorded on the worksheet.  Finally a brief discussion arriving at an explanation of what happened ends the activity.

We have found that once we have run such a workshop at a school,  the teacher is able to repeat the workshop for other classes.  The activities described below have been chosen not only because they make use of simple apparatus but mainly for the fact that they work!  The physics demonstrated by the activities is on the whole beyond that in the school physical science syllabus but we have found that this is not a hindrance to the success of the workshops. We have tried a number of other activities and those that we describe below are the ones that we have experienced to work best.  Many of these activities, and others, may be found in the resource books listed at the end of this paper.  We are, of course, eager to receive suggestions and ideas to expand the list we have presented here.
 

The activities.

1.   Place two empty cold drink cans on a flat smooth table about 3 cm apart and blow between them parallel to the surface of the table.  The cans move together demonstrating Bernoulli’s Principle that the pressure is lowest where the velocity of air is greatest.

2.  Another activity demonstrating Bernoulli’s Principle is to hold one drinking straw vertically in a beaker of water and blow across the open end with a second straw.  The water rises in the first straw and then may spray out (like an aerosol spray) if the straws are short enough.

3.  A final Bernoulli activity is to place a  20c  coin and a saucer on a flat surface about
10 cm apart.  Blowing hard across the top of the coin should cause it to skip into the saucer (with a little practice).

4.  This is one of our favourites.  Inflate a balloon about halfway and connect the end to a short piece of  hose pipe (about 5 cm long), being careful not to let any air out.  Inflate a second balloon just a little bit and connect it to the other end of the pipe.  When the air is allowed to flow from one balloon to the other, it is surprising to many to see that balloon with more air in gets even bigger. The balloon with less air in forces its air out due to the relatively stronger elastic forces acting on its volume.

5.  Inflate a balloon and release it to fly around the room.  After discussing why the balloon is propelled, ask the question whether or not the same explanation is valid if the balloon was let free on the moon.

6.  Make a simple balance by putting a long nail through the centre of a 30 cm long, thin wooden stick.  Take two weights of about  250 g  and tie each to a piece of string which in turn are tied to each end of the balance. Hold the nail so that the stick is free to rotate and adjust the distance of the strings from the nail so that the stick is balanced and remains horizontal.  Lower one weight into a beaker of water and the balance will tilt, demonstrating the effect of the buoyancy force.

7.  Make three holes in the sides of a polystyrene cup, each at a different height.  Fill the cup with water and place it on a flat surface.  When the water is allowed to flow out of the holes, the streams will hit the surface of the table at a distance depending on the amount of water above the hole.

8.  Partially fill a saucer with water and float 2 matchsticks on the water near the centre of the saucer.  Dip a third matchstick into some washing-up liquid and touch the surface of the water between the floating matchsticks.  The matchsticks in the water shoot apart as the surface tension is broken by the detergent.

9.   Ask the group why one shouldn’t water your garden in the blazing sun.  The effect of the drops of water acting as little lenses can easily be shown by placing a few drops of water on a page of text.

10.  The Cartesian diver is another favourite.  Fill a beaker with water and float a glass and rubber medicine dropper (the diver)  in the water.  Gradually draw water into the diver until it just floats in the beaker with its top at the surface of the water.  Fill a 2 litre cold drink bottle with water right to the top. Carefully transfer the diver to the 2 litre bottle and screw on the top tightly.  Squeezing the bottle will compress the bubble of air in the diver, thereby reducing the buoyancy force on the diver and allow it to dive. Experimenting with different divers with produce interesting results.

11.  Make two holes on each side of a polystyrene cup near the bottom. Fill the cup with water and release it from a good height.  The water does not flow out the sides of the cup while both the cup and the water are in freefall.

12.   Ask the group is whether or not a glass filled to the brim with ice and water will overflow as the ice melts.  This is easy to investigate.

13.  Take a long piece of string and tie on five or six  1 cm  diameter machine bolt nuts at regular distance intervals.  Hold one end of the string so that the first nut is just above the floor.  Release the string and the nuts with strike the floor and make a sound, but not at regular time intervals.  Ask the question how the nuts should be tied on so that the nuts are heard to strike the floor at regular time intervals.

14.  Balance a metrestick or ruler on your outstretched fingers.  Start with each finger at the ends of the ruler with the ruler resting on top.  Slowly move your fingers towards each other and you will find that they will always meet at the centre on the ruler.  The force of friction between the ruler and each finger depends on the relative lengths of ruler between each finger and end of ruler.

15. The concept of centre of mass can be introduced and explored with these two challenges.  Stand with your heels and back against a wall and try to touch your toes without lifting your heels.  Another is to stand with one shoulder and one foot against a wall and try to lift the other foot without losing your balance.  Both are impossible.

16.  Static electricity can be investigated with a role of plastic adhesive tape (Magic tape works best) and a few balloons.   Pull two strips of plastic adhesive tape of about 20 cm long from a roll.  Hold them by their ends and slowly bring them side by side and they should repel each other.  One at a time, pass each of the strips of tape lightly between your fingers, then hold the two strips near each other again and they should no longer repel each other.  Carefully stick the two strips to each other so that the sticky side of one strip sticks to the “dry” side of the other.  Now rapidly peel the strips apart and slowly bring them together again and they should now attract each other.  Various ways of peeling the strips off each other and other objects will yield interesting results.  Rubbing inflated balloons against each other and other objects like your hair is also interesting to explore. You can investigate the polarity of the strips of tape by rubbing a balloon in your hair (rubber always acquires a negative charge when touched to hair) and holding the balloon near the strip of tape being investigated.

17.  Take a piece of wire of about 30 cm and bend it into a small loop with a handle.  Now take a square piece of paper and fold it in half twice then open it up to form a filter and put it in the loop of wire.  If you hold the paper above a lighted candle, it will catch alight and burn. When the experiment is repeated but with the paper filter filled with water, the paper does not burn as all the heat goes into boiling the water.
 

Resource books.

1 Berry, D A. (ed)  1986.   A POTPOURRI OF PHYSICS TEACHING IDEAS.  American Association of Physics Teachers Publishing Department, College Park
2 Bohren,  C E.   1987.    CLOUDS IN A GLASS OF BEER.    Wiley, New York
3  Bohren, C E.     1991.   WHAT LIGHT THROUGH YONDER WINDOW BREAKS?    Wiley,  New York
4 Doherty, P.  &  Rathjen, D. (eds)   1991.   THE EXPLORATORIUM SCIENCE SNACKBOOK.   Exploratorium Teacher Institute,  San  Fransisco
5 Edge, R.    1981.    STRING AND STICKY TAPE EXPERIMENTS.    American Association of Physics Teachers Publishing Department, College Park
6 Epstein, L C.   1986.   THINKING PHYSICS.   Insight Press, San Francisco
7 Freier, G D.  &  Anderson, F  J.   1981.    A DEMONSTRATION HANDBOOK FOR PHYSICS IDEAS.   American Association of Physics Teachers Publishing Department, College Park
8 Robinson, P.   1993.    CONCEPTUAL PHYSICS LABORATORY MANUAL 7th ed.  HarperCollins College, New York
9 Walker, J.   1977.    THE FLYING CIRCUS OF PHYSICS WITH ANSWERS.   Wiley, New York