Intro to Physics

1. Intro to Physics

2. Scientific notation Scientific notation is a system that makes it easy to work with the huge range of numbers needed to describe the physical world. Even very large or very small numbers can be simply expressed as a coefficient multiplied by a power of ten.

3. Scientific notation Scientific notation is a system that makes it easy to work with the huge range of numbers needed to describe the physical world. The coefficient is a decimal number between 1 and 10.

4. Scientific notation Scientific notation is a system that makes it easy to work with the huge range of numbers needed to describe the physical world. Powers of tenare 10, 102 = 100, 103 = 1000, 104 = 10,000 and so on. The coefficient is a decimal number between 1 and 10.

5. Numbers less than one For numbers less than one, scientific notation uses negative exponents: The number 0.0015 is 1.5 ÷ 1000 = 1.5 × 10-3

6. Powers of ten

7. Powers of ten on a calculator Calculators and computers use the symbol E or EE for powers of ten. The letter E stands for “exponential” (another term for scientific notation).

8. Practice… Use the calculator to write numbers in scientific notation: 4,180 joules 0.035 meters -2 3.5 0.035 4.18 x 103 joules (4.18 E3) 3.5 x 10-2 meters (3.5 E-2) 3.5 E-2 3.5 e-2 3.5 ee-2

9. Express the following numbers in scientific notation: • 275 • 0.00173 • 93,422 • 0.000018 Assessment

10. Express the following numbers in scientific notation: • 275 2.75 x 102 • 0.00173 1.73 x 10-3 • 93,422 9.3422 x 104 • 0.000018 1.8 x 10-5 Assessment

11. Importance of Units • In Physics units are a key to telling you what sort of quantity you’re dealing with. • Having the units we use memorized will be vital to your success this year! • Unless you’re told otherwise EVERY answer you have this year should have UNITS with it! Units are like clothes for your #’s, we do NOT want any naked #’s! • Example You calculate that a ball traveled a distance of 5 meters. • WRONG way to record answer  5 • RIGHT way to record answer  5m or 5 meters

12. The International System of Units

13. Measuring mass In the SI system, mass has units of grams (g) and kilograms (kg). One kilogram is 1000 grams.

14. Length • Length is a fundamental quantity. There are two common systems of length units you should know: • The English system uses inches (in), feet (ft) and yards (yd). • The metric system using millimeters (mm), centimeters (cm), meters (m), and kilometers (km). The meter is the SI base unit for length.

15. Surface area Area is a derived quantity based on length. Surface area describes how many square units it takes to cover a surface. All surface area units are units of length squared (for example: m2).

16. Volume Volume is another derived quantity based on length. It measures the amount of space, in units of length cubed. (example: m3)

17. Density Density is an example of a derived quantity. It measures the concentration of mass in an object’s volume. The symbol for density is this Greek letter, rho: ρ Density Tower - video Why did the tower make layers and not mix together?

18. Solving for Density A delivery package has a mass of 2700 kg and a volume of 35 cubic meters. What is its density? 77 kg/m3

19. Calculating density When calculating derived quantities, it will be important to use consistent SI units. For example: If density in kilograms per cubic meter is desired, then the mass must be in kilograms, and the volume must be in cubic meters.

20. Time Time is a fundamental quantity. The SI unit of time is the second.

21. Converting units When solving physics problems, the units you use must be consistent. You need to be able to convert units to make them consistent. To convert a quantity from one unit to another, multiply by a conversion factor. A conversion factor always has the value of one (1) whether it is right-side-up or upside-down.

22. Converting units Here are some examples of conversion factors for length.

23. Converting other units To convert from one unit to another, multiply by the appropriate conversion factor. • Pick the conversion factor that lets you cancel the unit you don’t want, and end up with the unit you want. • You’ll always “cancel” things diagonally

24. Test your knowledge Use the conversion factor shown at right to convert 12 inches to centimeters.

25. Test your knowledge Use the conversion factor shown at right to convert 12 inches to centimeters. Flipping the conversion factor upside down lets you cancel the unit you don’t want, and end up with the unit you want.

26. Converting Fractions • Converting values in fractions is a little different • Ex 1: Convert 10m/s to cm/s. • Ex 2: Convert 10m/s to m/hr.

27. Example 1 • Convert 10m/s to cm/s.

28. Example 2 • Convert 10m/s to m/hr.

29. Double conversions • Convert 10mi/hr (i.e. mph) to m/s

30. Which of the following unit conversions is correct? Assessment A. B. C.

31. Which of the following unit conversions is correct? Assessment A. B. C. If this is a final answer, round to the correct number of significant figures.

32. Solving for a variable Suppose this is the formula: But the variable you are asked for is time t.

33. Solving for a variable Solve the relationship for time, t : Multiply both sides by 2: (To get rid of a fraction you “flip & multiply”)

34. Solving for a variable Solve the relationship for time, t : Multiply both sides by 2: (To get rid of a fraction you “flip & multiply”) Divide both sides by a:

35. Solving for a variable Solve the relationship for time, t : Multiply both sides by 2: Divide both sides by a:

36. Solving for a variable Solve the relationship for time, t : Multiply both sides by 2: Divide both sides by a: Take the square root of both sides:(Square root will get rid of a square)

37. Solving for a variable Solve the relationship for time, t : Multiply both sides by 2: Divide both sides by a: Take the square root of both sides:(Square root will get rid of a square)