Physics investigations for May 2006 candidates: instructions for students

You may, but are not required to, also look for more information about the theoretical background of the investigations in the school library or on the net (e.g. the teachers' instructions at the IB Physics Compendium site. If there is time left after completing the tasks given below, try to improve and develop the investigations, possibly into an idea for an Extended Essay!

Pre-DP investigations

Course 1.

1. Walking speed of pedestrians. (as fast along street as across it)

2. Falling motion with stopwatch. (one height, s = ½at2 to find a = g)

Course 2.

3. Friction

4. Rolling car onto floor, find initial velocity (s = t(u+v)/2, v = 0, is it dependent on ...?.

Course 3.

5. Projectile motion with a rubber band (compare .

6. Find torque => force of friction of door, OH-mirror or other

Real-DP investigations

1. Find the density of a given liquid using the same method as in the given model report. Study the report and discuss what could be improved in it.

2. Let a piece of chalk, a small ball or some other suitable object roll from rest along a somewhat inclined table or other surface. Find its acceleration from measurements of time and displacement (recall pre-DP-investigation 2) . Compare this to a value predicted from calculations based on the angle of inclination of the table and the gravity acceleration.

3. Produced a set of time-distance data points which describe a person walking in the corridor. Produce a spreadsheet which presents the measured time values (variable x), the measured distance values (variable y_exp), and distance values calculated from the measured time values as y_model = kx. Use absolute and relative cell references (the teacher or other group members will assist you if necessary). Let the spreadsheet produce a graph of y_exp and y_model as functions of x in the same diagram. Adjust k until the graphs coincide. What quantity does k represent in this model? What assumptions is the model based on?

4. Investigate a given spring using the same method as in the given model report. Study the report and discuss what could be improved in it.

5. Fill a 500 ml separation funnel with water, let the water flow out of it and investigate the following research questions:

I. How does the flow of water (e.g. in milliliter per second) vary with time?

II. How does the flow of water vary with the depth?

III. What type of motion - uniform, uniformly accelerated or other - is the vertical motion of the water surface as the water flows out?

Discuss in the group how to take measurements and how to process them in order to answer these questions.

5. Use the Empirica data-logging equipment (ultra-sound position detector) to study falling motion and find a value for g. The detector signal must be reflected from a flat surface (phone book, manual etc.)

6-I. Investigate a simple (or other) pendulum. This investigation will be assessed on all criteria.

7. 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.

8. 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.

9-II. Investigate static friction. This investigation will be assessed on all criteria.

10. A. 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.

B. 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.

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

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. Find the volume expansion coefficient of ethanol and/or water. The relevant formula is not required in the IB programme, but given in the Compendium. Search the net or school library for a "known" value for it.

20. Use a laser and a transparent container to experimentally determine the refractive index of 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.

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

23-III. Investigate a DC circuit. This investigation will be assessed on all criteria. (Note: find a research question other than the internal resistance and emf of a battery, which will be done in investigation 24).

24. 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.

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.

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.

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.

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. Historical physics:

32. Biomedical physics:

A. Determine where the center of gravity in humans is using a bathroom scale and a ca 2-3 m long plank. Put the plank horizontally with one end on the scale and the other on some supporting object (phonebook). The human is placed horizontally on the plank and conditions for mechanical equilibrium applied.

B. Measure the blood pressure with the blood pressure meter first at the heart level, then from the arm or leg keeping it at different levels. Investigate the differennce in pressure and compare it to a theoretical value based on the formula for hydrostatic pressure (p = p₀ + dgh).

33. Relativity : Find a relativistic version of Newton's II law by using the form F = dp/dt differentiating p = gm₀v (the teacher will help you with the differentiation process if necessary). Then use this to construct an Excel spreadsheet to simulate the linear acceleration from rest of an object affected by a constant net force.

34. Astrophysics : Construct a simple quadrant to measure the altitude above the horison of an astronomical object. Observe and sketch ca 20 stars visible to the naked eye in some area of the sky. Measure the altitude and approximate azimuth of some bright star in the selected 20 to facilitate identification of them with the SkyMap program. Also note the time and place for the observation. Identify the stars with SkyMap, take the visual magnitude value for them from the program and find the maximum magnitude visible. Compare the result for different locations (city, country) and find the limiting brightness value.

35. Optics :

.