Introduction
Performance assessments in physics are tasks I would like my high school physics students to be able to do in front of me if I asked them to. What follows is a list of those tasks, the materials needed for the tasks, and a possible solution for each task. This list is a DRAFT because the tasks are--as yet--untried and untested as performance assessments. I welcome your input as to what additions or modifications would propose to improve this list.
Linear Kinematics in One Dimension
1. Task: Determine the speed of an object in uniform motion.
Materials: Meterstick, stopwatch, uniform motion object.
Possible solution: Use stopwatch to measure time interval needed for an object to travel a specific distance (measured with the meterstick), use v=d/t. Bonus for correct use of significant figures.
2. Task: Determine the acceleration of an object in uniform accelerated motion.
Materials: Meterstick, stopwatch, uniform acceleration object.
Possible solution: Use stopwatch to measure time interval needed for an object to travel a specific distance (measured with the meterstick). Divide distance by interval to determine speed. Bonus for correct use of significant figures.
3. Task: Construct Kinematics graph-matching "roller coaster."
Materials: Ball that can roll freely inside... 2m of flexible clear plastic tubing, support rods and clamps, clamps to hold tubing, kinematics graph to match.
Possible solution: Arrange the clamps to hold the tubing in place in a pattern that will allow the ball to roll so that its motion matches the graph.
Linear Kinematics in Two Dimensions
4. Task: Roll a ball down a ramp and off a table so that it lands in a cup.
Materials: Ball, ramp, cup, meterstick.
Possible solution: Students practice by rolling the ball from various heights along the ramp and measuring the corresponding landing distance. The cup is then placed by the instructor and the students must decide where along the ramp to launch the ball so that it will land in the cup. A bullseye (with carbon paper) can be used in place of the cup.
Forces
1. Task: Determine the coefficient of kinetic friction between a block and a board.
Materials: Board, block, known masses, spring scale.
Possible solution: Measure weight of block and force needed to keep it moving on the (level) board at a constant speed, use µk = F/mg. Bonus for correct use of significant figures.
2. Task: Determine the coefficient of static friction between a block and a board.
Materials: Board, block, protractor.
Possible solution: Place block on board, tilt board up until block begins to slide, measure angle at which sliding occurs, use µs = tanq (students must show why this is a valid calculation). Bonus for correct use of significant figures.
3. Task: Determine the aerodynamic coefficient of a coffee filter.
Materials: Coffee filter, balance, meterstick, stopwatch.
Possible solution: Time fall of filter from significant height to determine terminal speed, use k = mg/v2. (The aerodynamic coefficient k = (1/2)rCA.) Bonus for correct use of significant figures.
Energy
1. Task: Determine the gravitational potential energy and kinetic energy of a a pendulum bob.
Materials: Pendulum with cylindrical (not spherical) bob, photogate timer, meterstick.
Possible solution: Measure bob's height above equilibrium and use PE = mgh for potential energy, measure bob's width and time through photogate timer (in GATE mode) at equilibrium, use KE = (1/2) m(d/t)2. Bonus for correct use of significant figures.
Rotation
1. Task: Determine the mass of object using meterstick balance.
Materials: Meterstick, fulcrum, knife edge, hanger clamps, mass hangers, slotted masses, unknown.
Possible solution: Construct a balance, balance unknown with known masses, collect lever arm and weight data for various balanced arrangements, use mu = mkdk/du. Bonus for correct use of significant figures.
Electrostatics
1. Task: Determining the charge of an object.
Materials: Electroscope, electrophorus, plastic strips, cloth swatches.
Possible solution: Place a strip of charged vinyl (known to be negative) on the electroscope to cause a deflection of the pointer, bring object with unknown charge near (but not touching) electroscope and observe reaction, increased deflection indicates object is negative, decreased deflection indicates object is positive.
2. Task: Determining the charge on an electroscope.
Materials: Electroscope, electrophorus, plastic strips, cloth swatches.
Possible solution: Electroscope is charged by instructor. Bring a strip of charged vinyl (known to be negative) near the electroscope and observe reaction, increased deflection indicates charge on electroscope is negative, decreased deflection indicates charge on electroscope is positive.
Current
1. Task: Determine the resistance of on unknown resistor.
Materials: Power supply, wires, voltmeter, ammeter, unknown.
Possible solution: Connect a circuit using the power supply, connecting wires and unknown resistor, use ammeter and voltmeter to collect current and voltage data, use R = V/I. Bonus for correct use of significant figures.
2. Task: Characterize the relationship between temperature and resistance of a light bulb filament.
Materials: Power supply, connecting wires, voltmeter, ammeter, flashlight bulb (miniature bulb) in miniature socket.
Possible solution: Connect a circuit using the power supply, connecting wires and unknown resistor, use ammeter and voltmeter to collect current and voltage data, use R = V/I and P = VI, plot Resistance versus Power.
Circuits
1. Task: Light a bulb using a battery and a wire
Materials: Flashlight bulb (miniature bulb), battery, connecting wire.
Possible solution: Arrange wire to connect both terminals of battery to both conducting surfaces of bulb.
2. Task: Construct a three-bulb circuit that will be as bright as three bulbs can be.
Materials: Miniature bulbs, miniature sockets, battery, connecting wires.
Possible solution: Arrange bulbs in a series circuit.
3. Task: Construct a three-bulb circuit that will allow the longest life for the battery.
Materials: Miniature bulbs, miniature sockets, battery, connecting wires.
Possible solution: Arrange bulbs in a series circuit.
4. Task: Construct a three-bulb circuit so that if one bulb fails, the other two fail.
Materials: Miniature bulbs, miniature sockets, battery, connecting wires.
Possible solution: Arrange bulbs in a series circuit.
5. Task: Construct a three-bulb circuit so that if one bulb fails, the others remain lit.
Materials: Miniature bulbs, miniature sockets, battery, connecting wires.
Possible solution: Arrange bulbs in a parallel circuit.
6. Task: Construct a three-bulb circuit so that if one bulb fails, the others remain; if two bulbs fail, the last bulb fails
Materials: Miniature bulbs, miniature sockets, battery, connecting wires.
Possible solution: Arrange bulbs in a compound circuit.
Magnetism
1. Task: Determine the arrangement of bar magnets based on a pattern of iron filings.
Materials: Bar magnets, iron filings (loose or in projectual), paper or towel (or equivalent).
Possible solution: Observe pattern of iron filings over an unseen arrangement of bar magnets, by recognition of "attraction" and "repulsion," the general polarity of magnets can be determined (although specific north and south polarities cannot).
2. Task: Determine the direction of DC current in a wire based on compass behavior.
Materials: Battery, connecting wire, directional compass.
Possible solution: Arrange the wire and compass so that the current passes over the compass in a north-south direction, observe deflection of the compass needle when the current flows, use the right-hand rule to determine the direction of current.
Simple Harmonic Motion
1. Task: Determine the force constant of a spring using masses and meterstick.
Materials: Spring (10N/m < k < 100N/m), slotted masses and mass hanger (or equivalent), meterstick, support rods and clamps.
Possible solution: Attach mass to the spring, measure stretch, use k = mg/x. Bonus for correct use of significant figures.
2. Task: Determine the force constant of a spring using masses and stopwatch.
Materials: Spring (10N/m < k < 100N/m), slotted masses and mass hanger (or equivalent), stopwatch, support rods and clamps.
Possible solution: Time ten oscillations to determine period, use k = m(2/T)2.
3. Task: Determine an unknown mass using a spring and a meterstick.
Materials: Spring with known force constant (10N/m < k < 100N/m), slotted masses and mass hanger (or equivalent), meterstick, support rods and clamps.
Possible solution: Attach mass to the spring, measure stretch, use m = kx/g. Bonus for correct use of significant figures.
4. Task: Determine an unknown mass using a spring and a stopwatch.
Materials: Spring with known force constant (10N/m < k < 100N/m), slotted masses and mass hanger (or equivalent), stopwatch, support rods and clamps.
Possible solution: Time ten oscillations to determine period, use m = k(T/2)2. Bonus for correct use of significant figures.
Waves
1. Task: Determine the frequency of an unknown tuning fork.
Materials: Tuning fork (with frequency information obscured) and mallet, adjustable resonance column apparatus, meterstick.
Possible solution: Strike fork and place near opening of air column, adjust length of column until resonance is achieved, measure length of air column and diameter, use f = v/4(L + 0.04d). Bonus for correct use of significant figures.
Light
1. Task: Determine the index of refraction of an unknown transparent substance.
Materials: Semicircular cell, transparent substance (syrup, soft soap, etc.), protractor, corkboard or equivalent, pins.
Possible solution: Place semicircular cell (partially filled with transparent liquid) on corkboard, place a pin vertically in the corkboard a few centimeters in front of the flat side of the cell, look through curved side of the cell and align the pin with the scratch at the midpoint of the flat side of the cell, place another pin in the corkboard behind the curved side, measure angles of incidence and refraction and use n = sinq1/sinq2. Bonus for correct use of significant figures.
Geometric Optics
1. Task: Determine the focal length of a converging mirror or converging lens.
Materials: Converging mirror or lens, light source, meterstick, screen. Optical bench recommended.
Possible solution: Arrange object, lens, and screen to form an image, measure object distance and image distance, use 1/f = 1/o + 1/i. Bonus for correct use of significant figures.
Physical Optics
1. Task: Determine the slit spacing on a diffraction grating or the groove spacing on a compact disc.
Materials: Laser with a known wavelength, diffraction grating with unmarked slit spacing or compact disc, metersticks, support rods and clamps.
Possible solution: Pass laser beam through grating to produce a pattern, measure distances to first-order (and perhaps second-order) maxima, calculate angle(s) and use d = ml/sinq. Bonus for correct use of significant figures.
2. Task: Determine the wavelength of a laser using a diffraction grating.
Materials: Laser with unmarked wavelength, diffraction grating with slit spacing marked, metersticks, support rods and clamps.
Possible solution: Pass laser beam through grating to produce a pattern, measure distances to first-order (and perhaps second-order) maxima, calculate angle(s) and use l = (d/m)sinq. Bonus for correct use of significant figures.
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