Physics investigations for May 2005 candidates

1. Let a piece of chalk, a small ball or some other suitable object roll from rest along a somewhat inclined table or other surface. Produce a set of data points (at least 5) which can be used to make a graph of displacement as a function of time for the object. Calculate and graph the average velocities between the data points. Using the average velocities, find an approximate value for the acceleration. What do you thing the acceleration should be?

2. Plan and do an experiment to find the relation between water depth and rate of water flow (milliliters per sec.) from a separation funnel.

3. Determine the gravity acceleration g using a small falling object, a stopwatch, and other simple equipment you find necessary.

4. Use the Empirica data-logging equipment (ultra-sound position detector) to study falling motion and find a value for g. 

5. To study falling motion where air resistance is significant, make an air-filled balloon (possibly with a very small weight attached to it). Plan an experiment to find out roughly after what falling distance it reaches its terminal velocity.

6. Investigate projectile motion using a rubber band. Produce a graph of range as a function of the angle to the horizon of the initial velocity (which angle gives the maximum range?). Search the literature in the school library for a theoretical analysis of projectile motion and try to produce a corresponding graph based on this. Compare and discuss the graphs.

7-I. Investigate the phenomenon of static friction by choosing one or more variables which according to the course theory either should or should not affect the force of friction. Plan an investigation to find if this can be supported by experimental evidence, paying special attention to the involved uncertainties.

8. Investigate how the length and mass of a simple pendulum affect its time period. Also measure the gravity constant g using the pendulum and literature about it if necessary.

9. Let a small car roll down a slope and onto the floor until it stops. Plan a and try out a way to find the coefficient of rolling friction specific to this car using measurements of time and distances assuming it follows a formula similar to the one for sliding or static friction. Repeat the experiment several times and for different masses/ and or initial positions for the car.

10. Let a small car roll down a slope and out onto the floor until it stops. Plan a way to determine the rolling friction coefficient. Repeat the experiment several times and for different masses/ and or initial positions for the car using only distance measurements. Combine this information with the result from investigation 9 and discuss how well the results obtained with the different methods agree, taking into account relevant uncertainties.

11. Put a small object in horizontal circular motion using a tube and a metal weight which provides the centripetal force. Calculate this force based on the experimentally determined speed of the small object and compare this value to the weight of the metal piece.

12. Find out from where a small metal ball must start to complete a loop in a given metal track (make a sketch of the given equipment) without falling out of it. Compare this to a value based on the radius of the loop.

13. Compare the cooling process of hot water in vessels covered with shiny metal foil and vessels covered with black paper/ other black and shiny vessels. Also study the heating in them using an infrared lamp.

14. Compare the rate of cooling per thickness and/or surface area for vessels made of different materials (metal, glass or ceramic, plastic) or with different thickness.

15. Heat two identical glass beakers, one filled with water and one with water mixed with potato flour. Measure the temperature as a function of time and suggest a mechanism to explain any differences.

16. Construct a spreadsheet which calculates and graphs a) the rate of cooling as a function of time b) the rate of cooling as a function of temperature given a set of time-temperature data points. Analyse the results of investigations 13-15 with it.

17. Search the Internet for instructions on how to build a psychrometer to measure relative air humidity. Discuss and test a hypothesis about how the results would differ if a different liquid than water is used (e.g. ethanol).

18. Plan and conduct an experiment to find the efficiency of a microwave oven (the efficiency in converting the energy in the microwaves as reported by the manufacturer to thermal energy in the heated food or drink, not the efficiency in converting electrical energy to energy in the waves)

19-II. Plan and carry out an investigation to determine some quantity which describes the behaviour of a liquid at different temperatures (e.g. volume expansion coefficient, freezing point, boiling point, specific heat capacity or other).

20. Use a laser and a transparent container to experimentally determine the refractive index and critical angle for total internal reflection for water and/or other liquids.

21. Simulate the interference between two "one-dimensional" wave motions in a spreadsheet using the equation for the displacement of an oscillator x(t) = Asin(2pft + phase shift). Investigate the "beat" phenomenon, what formula for the beat frequency is valid, whether and how it depends on the phase shift. Also investigate possible beat phenomena for 3 or more waves interfering.

22. Determine the wavelength of a He-Ne-laser light using diffraction gratings with known numbers of lines per mm. Search the Internet for information about the 'correct' value.

23-III. Investigate some freely chosen quantitative electric property of a DC circuit you construct. Pay attention to all relevant types of errors and uncertainties.

24. Construct different series and parallel circuits and investigate with a digital ohmmeter how the total (equivalent) resistance measured compares to a theoretical value. Also observe how the potential difference is distributed in the different circuits and try to express it verbally in a general law. Alternatively (if this investigation is too similar to what you already did in Inv. 23): same job with capacitors and the digitial faradmeter (not needed in the IB, but part of the national curriculum).

25. Investigate the qualitative and/or quantitative properties of the magnetic field outside a current-carrying solenoid using a simple orienteering compass to "measure" the field intensity. Pay attention to which simplifying assumptions are necessary and can be justified.

26. Determine the internal resistance and emf of one or more batteries graphically by connecting different resistors to them and measuring the current through and potential difference over the external resistor.

27. Determine the magnetic field strength B between the poles of an U-shaped magnet using the torque on a current-carrying wire arranged so that the torque can be approximately found with the help of the deflection angle and the mass per length of the wire. Pay attention to the necessary simplifications and discuss if a more accurate value would be higher or lower than the one you get with this method.

28. Construct a simple transformer and investigate briefly its function testing the formulas in the corresponding section in the textbook; then turn it into a metal detector by rotating one of the coils 90 degrees. Investigate what minimim amount of metal it reacts to. Alternatively: study the functioning of a cathode ray oscilloscope and how its display is distorted by external magnetic fields from bar magnets or current-carrying solenoids. Estimate the potential difference between the back of the CRT and its screen based on observations.

29. Search the available libraries and other sources for information about the history of the atomic model. Which parts of physics were relevant for supplying arguments for the atomic model? How did physics interact with other sciences (e.g. chemistry)? Why did some oppose the atomic model in the 19th century? What arguments for the atomic model would we today present to an alien civilisation not believing in it?

30. Construct a spreadsheet which simulates a radioactive decay series where the nucleus X with the half-life T_x decays into Y which with the half-life T_y decays into Z, which is stable. Vary the half-lives and the initial amounts of the nuclei (N_x, N_y, N_z) and report any non-trivial phenomena the simulation reveals.

31. and 32: Investigations relating to the options chosen later.