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CRITICAL THINKING

CRITICAL THINKING. The Eiffel Tower has a mass of 10,000,000 kg. A 100:1 scale model of the tower made from the same material will have a mass of (A) 100,000 kg (B) 10,000 kg (C) 1,000 kg (D) 100 kg (E) 10 kg (F) 1 kg.

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CRITICAL THINKING

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  1. CRITICAL THINKING

  2. The Eiffel Tower has a mass of 10,000,000 kg. A 100:1 scale model of the tower made from the same material will have a mass of (A) 100,000 kg (B) 10,000 kg (C) 1,000 kg (D) 100 kg (E) 10 kg(F) 1 kg • The paths crossed for three men -- A, B, and C -- walking through woods. It was a cold night. They decided to light a fire and rest by it for the night. They set out to bring some firewood. A came back with 5 logs of wood, B brought 3 logs, but C came back empty-handed. C requested that they let him rest by the fire and promised to pay them some money in the morning. In the morning C paid them $8. How should A and B split the money fairly? (A) A $7; B $1(B) A $6; B $2(C) A $5; B $3(D) A $4; B $4(E) None of these

  3. An insect is climbing up a 30 ft. vertical wall. Starting from the bottom, the insect climbs up 3 ft. during the day and slips down 2 ft. during the night. In how many days will the insect reach the top of the wall? (A) 31 days (B) 30 days (C) 29 days (D) 28 days (E) 27 days (F) Never • Two trains are moving toward each other with speeds of 17 mph and 43 mph. How far apart are they 1 minute before they pass each other? (A) 60 miles (B) 30 miles (C) 6 miles(D) 3 miles (E) 2 miles (F) 1 mile

  4. Weight of the Flies. The weight of a closed jar is W while the flies inside it are flying around. What will be the weight of the jar if the flies settle down inside the jar? (A) Equal to W(B) Less than W(C) Less than W

  5. INTRODUCTION TO PHYSICS NCEA LEVEL 2

  6. The physics course is made up of three main areas of study PHYSICS BASICS

  7. PHYSICAL QUANTITIES The study of Physics requires us to measure physical quantities and UNITS are used to denote what quantities we are measuring. It is important that after every measurement we place a UNIT to state what we are measuring otherwise the quantity measured is useless. There are 7 units for measurement. Devised by the Systeme International d’Unites’. These are specific units for specific measurements.

  8. SI units are based on 3 fundamental quantities • Mass kg. M. • Length m. L. • Time s. T. Area =L x L = L² Velocity = L / T = LT-1 Energy = ½ mv² = M x ( L/T) ² =ML²/T² = units joules

  9. Often the size of the quantity Physicists measure is very large or very small. To help make the numbers easier to use prefix multipliersare used. You know it as standard form. These are mulitples of ten. You must learn these and be able to convert from one to the other. The standard prefix multipliers are:

  10. Giga Mega Kilo Milli Micro Nano Pico If positive power, move decimal place to the right. If negative power, move decimal place to the left  Is the Greek letter pronounced ‘mew’

  11. Example Questions • Solutions: • 8 km = 8 x 103m • = 8000m • 1 kg = 1 x 103g • = 1 x 103 x 106g • = 109g • 2.8 x 1010W = 2.8 x 10 x 109W • = 28 x 109W • = 28 GW 1. Change 8 km to m 2. How many micrograms are there in a kilogram? 3. Write 2.8x1010 watts in gigawatts

  12. SIGNIFICANT FIGURES

  13. Rules for Processing Data

  14. Example: • SOLUTION • Perimeter of the plate: • = 15.4 + 0.94 + 15.4 + 0.94 • = 32.68 • = 32.7 cm (to 1 decimal point) • Area of the plate: • = 15.4 x 0.94 • = 14.476 • = 14 cm2 (to 2 sf)

  15. EXERCISES

  16. DATA ERROR As Physicists you now have to question the validity of the data you collect. Can you accept it or should you do it again. When looking at error we firstly have to deal with whether there is an error in the first place. Two terms that should be employed when looking at data are PRECISE and ACCURATE.

  17. What do these terms mean: • PRECISE : • cluster of data but possibly in the wrong place. • ACCURATE : • data which is grouped around the right place. • ACCURATE & PRECISE: • data which is clustered in the right place and close together.

  18. Precise or Accurate?? This is a random like pattern, neither precise nor accurate. The darts are not clustered together and are not near the bull's eye.

  19. Precise or Accurate?? This is a precise pattern, but not accurate. The darts are clustered together but did not hit the intended mark.

  20. Precise or Accurate?? This is an accurate pattern, but not precise. The darts are not clustered, but their 'average' position is the center of the bull's eye.

  21. Precise or Accurate?? This pattern is both precise and accurate. The darts are tightly clustered and their average position is the center of the bull's eye.

  22. There are two types of error • Random error - are statistical fluctuations (in either direction) in the measured data due to the precision limitations of the measurement device. Random errors usually result from the experimenter's inability to take the same measurement in exactly the same way to get exact the same number. • Systematic error - by contrast, are reproducible inaccuracies that are consistently in the same direction. Systematic errors are often due to a problem which persists throughout the entire experiment.

  23. Identification of these random and systematic errors and how you go about alleviating them is a major component of your internal 2.1 achievement standard.

  24. How do we improve the accuracy of our measurement? • Take repeated readings and average them • Take a multiple measurement of some quantity and then divide by the number of items being measured • Adjust the zero reading or subtract value from the readings when using that instrument • Read directly from in front of the scale

  25. Systematic and random errors refer to problems associated with making measurements. Mistakes made in the calculations or in reading the instrument are not considered in error analysis. It is assumed that the experimenters are careful and competent!

  26. Skills Practical • 1. Microscope slide • 2. Number of rice grains • 3. Time period of pendulum • Complete the questions on worksheet • Focus on: random and systematic errors and using the correct number of sf’s. • Pairs or individually • Finish questions for HW

  27. CONVERTING RELATIONSHIPS TO EQUATIONS GRAPHING SKILLS In order to produce an equation from data the following steps should be observed:

  28. Common Graphs • y  x • y  1/x • y  x² • y  1/x²

  29. Y is proportional to X • When X changes by certain factor, Y changes by the same.

  30. Y is inversely proportional to X • When X is multiplied by a certain factor, Y is divided by the same factor

  31. Y is proportional to the square of X • As X is multiplied by a certain factor, Y is multiplied by the square of that factor

  32. Y is inversely proportional to the square of X • As X increases by a certain factor, then Y decreases by 1/ the square of that factor • E.g. X doubled, Y decreases by 1/4

  33. Using these skills do exercises from Page: 10 -20 RUTTER

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