difficulties and improvements 物理实验中存在问题与解决方案讨论.doc

Source of error: two sets of readings are not enough to draw valid conclusion.Improvement: Take more readings and plot a graphMeasuring height of water/depth of water:Source of error: Difficulty to measure height owing to refraction effects (shape of bottle).Improvement: Add dye Use paper behind the bottleUse mirror behind bottleSet up the apparatus:Source of error: Difficulty in setting up the line/ruler/strip horizontally or vertically:Improvement: Use set square on the bench to ensure that . is horizontal or vertical.Measure each end of rule to see if distance about bench is the same.Measuring height (including height of water) or length in vertical direction:Source of error: Parallax error in measuring hImprovement: Use set square from ruler to .to indicate heightget eye level perpendicular to the ruler scaleplace the ruler as close as possible to the put scale onto bottleMeasuring distance in horizontal separation:Source of error: Parallax error in measuring dImprovement: Place ruler under path and use shadow projectionUse set square as markers, place ruler under path and view vertically from aboveMeasuring lengthSource of error: Parallax error in reading the lengthImprovement: place scale on the bladeDeciding an instant:Source of error: difficulty to measure h as the ball is moving quickly.Improvement: Use video camera and play back with slow motion to measure h accurately.Source of error: difficulty in judging the end pointImprovement: mark the distance with lines on rampSize of increment:Source of error: difficulty in judging when the bottle was about to toppleImprovement: trial and error, bring bottle closer to point of toppling.Hold with newton meter and tilt until F=0Source of error: Poor accuracy due to size of incrementImprovement: use smaller incrementSource of error: Use of increments impreciseImprovement: Use smaller mass incrementsMeasuring angle:Source of error: difficulty in measuring angle owing to container not perfectly right angled at the bottom.Improvement: make bottle square with plasticine.Source of error: parallax error in measuring angle on the protractorImprovement: get eye level perpendicular to the protractor lines.Source of error: thick strings make measurement of angle hard.Improvement: use thinner strings/rulesSource of error: difficulty to accurately locate the center of knot.Improvement: use thinner stringsMeasuring diameter/radius:Source of error: .is not circular ( was flexible ), leading to an inaccurate value for diameter/radiusImprovement: use vernier caliper to measure diameter in different directions and average.Measuring time:Source of error: human error in timing.Improvement: Video the oscillations and play back frame by frameuse light gates to trigger a timerMeasuring period:Source of error: Oscillations are too quick to time manually.Improvement: Video the oscillations and play back frame by frameMeasure the time for a greater number of oscillations and average.Source of error: Difficulty in judging complete oscillation.Improvement: Use a fiducial marker to ensure the complete oscillation.Ensuring Center of massSource of error: difficulty in establishing center of mass of the ball(difficulty to measure l because it is hard to judge the position of center of the ball)Improvement: Find the mid-point of the mass by finding the distance to both ends and taking an average ( measure l to both ends of the ball and average)Mark the center of the ballReleasing the object:Source of error: difficulty to release the ball without applying a forceImprovement: Use a remotely operated clamp to release the ball.Use an iron ball and electromagnet to release it.Measuring length in circle:Source of error: The length of wire in one turn is different from the tube circumference because thread is spiral. Improvement: mark the wire and measure the straight length.measure the length in one turn by wrapping string, then unwrapping and measuring/workable method of getting even spacing of turns. Wrap so coils are closerUnwanted resistanceSource of error: contact resistanceImprovement: clean the contactsSource of error: lead resistanceImprovement: use shorter leadsreposition voltmeter connections closer to contactJudging the position for moveable contactsSource of error: difficult to judge whole number of turns when positioning contacts difficult to measuring 45cm length because wire not straightImprovement: use smaller plug /use smaller crocodile clipsmark lateral line on tube to give positions for contactsmeasure 45 cm with the wire straight, mark lateral line on wire to give positions for contactsFluctuation:Source of error: fluctuating current/ fluctuating voltmeter readingsImprovement: use smaller crocodile clips to connect the circuitInconsistence: Source of error: inconsistent bounce/inconsistent collisionsImprovement: use flat surface/use smoother brickSource of error: change in properties of thread due to repeated dropsImprovement: use a new thread each timeAir movement:Source of error: Motion of ball affected by air movementImprovement: turn off fansTurn off air conditionOperation:Source of error: Difficulty to hold both cylinders and tracing paperImprovement: Use clamps to hold cy