1. Copyright © 2010 Pearson Education, Inc. Chapter 1 Introduction to physics Dr. Haykel Abdelhamid Elabidi website: uqu.edu.sa/staff/ar/4331237 Email: haelabidi@uqu.edu.sa mobile: 0564518933 2 nd /3 rd week of September 2013/DhQ 1434

2. Copyright © 2010 Pearson Education, Inc. Course Syllabuls

3. Copyright © 2010 Pearson Education, Inc. Course Syllabuls

4. Copyright © 2010 Pearson Education, Inc. Units of Chapter 1 Physics and the Laws of Nature Units of Length, Mass, and Time Dimensional Analysis Significant Figures Converting Units

5. Copyright © 2010 Pearson Education, Inc. 1- What is Physics Physics is the study of the fundamental laws of nature. These laws can be expressed as mathematical equations. It is the science of measurements and experimental. Physicist (scientist who studies Physics) observes the phenomena of nature and try to find patterns and principles that relate these phenomena.

6. Copyright © 2010 Pearson Education, Inc. 2- Units of Length, Mass and Time To make quantitative comparison between the laws of physics and our experiments, certain basic physical quantities must be measured. We use here three basic quantities: length (L), mass (M) and time (T). We have to define the units used when measuring the three quantities: SI (International System of Units) or mks mks (m: meter, k: kilogramme and s: second) Mohamed measures the length of the room wall with a ruler, he gives us a value of 5. Abdullah measures the same length, he gives us a value of about 16. What is the real value of the length?

7. Copyright © 2010 Pearson Education, Inc. 2- Units of Length, Mass and Time Unit of Length: meter (m) One meter is the distance traveled by light in a vacuum in 1/299,792,458 of a second. See Table 1-1 page 3 Unit of Mass: kilogramme (kg) One kilogram is the mass of a particular platinum-iridium (Pt– Ir) cylinder kept at the International Bureau of Weights and Standards, France. See Table 1-2 page 3 Unit of Time: second (s) One second is the time required for a cesium(Cs)-133 atom to undergo 9,192,631,770 vibrations. See Table 1-3 page 4 The standard prefixes are used to designate common multiples in powers of ten. Exemples: 1mm =10 -3 m, 1km=10 +3 m, 1cm = 10 -2 m, 1micro= 10 -6 m,1angstrom = 10 -10 m See Table 1-4 page 5

8. Copyright © 2010 Pearson Education, Inc. 3- Dimensional analysis The dimension in physics refers to the type of quantity regardless of the unit used. Ex. a distance has a dimension of length, but the units can be meter or feet or mile… The dimension of a quantity is denoted in brackets: Length [L], Mass [M], Time [T] Any valid physical formula must be dimensionally consistent (each term must have the same dimensions) This type of calculation with dimensions is called dimensional analysis

9. Copyright © 2010 Pearson Education, Inc. 3- Dimensional analysis

10. Copyright © 2010 Pearson Education, Inc. 3- Dimensional analysis Exercise 1-2 page 5:

11. Copyright © 2010 Pearson Education, Inc. 4- Significant Figures The quotient d/t is calculated using a calculator displaying 8 digits: d/t=(21.5 cm)/(8.5 s)=2.4941176 cm/s The result must be less accurate than the two given numbers : RULE The number of significant figures after multiplication or division is equal to the number of significant figures in the least accurately known quantity. In our example: d is known to 3 significant figures t is known to 2 significant figures t is the least known quantity the speed should be given with 2 significant figures: d/t=2.5 cm/s 21.5 cm 8.5 s

12. Copyright © 2010 Pearson Education, Inc. Example 1-1 page 6: A tortoise travels at 2.51 cm/s for 12.23 s. How far does the tortoise go? only three significant figures 4- Significant Figures Answer: 2.51 cm/s × 12.23 s = 30.7 cm, and not 30.6973 cm You measure a time of 16.74 s, then you measure another time of 5.1 s The total measured time is 21.8 s, RULE The number of decimal places after addition or subtraction is equal to the smallest number of decimal places in any of the individual terms. and not 21.84 s

13. Copyright © 2010 Pearson Education, Inc. 4- Significant Figures

14. Copyright © 2010 Pearson Education, Inc. 4- Significant Figures

15. Copyright © 2010 Pearson Education, Inc. 2500 0.000036 Each of these numbers has two significant figures 2500 = 2.5 × 10 3 If we write 2.50x10 3, it has three significant figures 0.000036 = 3.6 x 10 -5 4- Significant Figures Exercise 1-4 page 7 How many significant figures are there in (a) 21.00, (b) 21, (c) 2.1x10 -2, (d) 2.10x10 -3 ?

16. 5- Converting Units We want to convert a distance of 225 ft to meters (m): We use the conversion factor 1m=3.281 ft and To make the conversion from feet (ft) to meters (m), we multiply 225 ft by the first factor (1 m/3.281 ft): To make the conversion of 24.3 meters (m) to feet (ft), we multiply it by the second factor (3.281 ft/1 m):

17. 5- Converting Units Convert the distance d=3.00 mi to meters. 1 mi=5280 ft First conversion: mi ft: Second conversion: ft m: We can do this in a single calculation:

18. 5- Converting Units Conversion involving any number of units: Conversion from hours to seconds: → The speed will be 9.84 ft/s You walk at 3.00 m/h, how fast is that in ft/s ? 1h=3600 s We need the conversion of 3.00 mi to meters (this was done before) and then the conversion of 1h to seconds.

19. 5- Converting Units You can see also Example 1-2 page 9 Active example 1-1 page 9: Blood in the human aorta can attain speeds of 35.0 cm/s. How fast is this in (a) ft/s and (b) mi/h? Solution:

20. Thank you for your attention See you next time Inchallah Homework: Ex.5; 6; 7; 8; 9; 11; 12; 13; 14; 15; 17 and 20 page 15