PHYSICS

Classical mechanics Electromagnetism Relativity Thermodynamics and statistical mechanics Quantum mechanics Theory and experiment Research fields Condensed matter Atomic, molecular, and optical High energy/Particle Physics Astrophysics Applied physics

Physics is the science of matter and its motion, as well as space and time — the science that deals with concepts such as force , energy, mass , and charge . As an experimental science , its goal is to understand the natural world.

We are going to deal with distance, velocity, and acceleration (kinematics and dynamics)

Measurement and Calculations

Measurement is very important in the field of physics. Mr. Mel weighs 120 kg. Is this the same as 120. or as 120.0 kg? - Measure line with ruler.

There is international agreement about the correct way to record measurements: RECORD ALL DIGITS THAT ARE CERTAIN, PLUS ONE UNCERTAIN (rounded) ONE. - these 'digits plus one' are called significant digits (Sig. digs.) and certainty is measured by the number of these digits.

Significant Digits Mathematician: 70/2 = 35 Physicist: 70/2 = 40 True or false: 1 + 1 = 3?

Significant digits … are used to provide the reader with an idea of the accuracy with which a measurement has been taken. Saying that a piece of wood is 12.00 cm long is different than saying that it is 12 cm long. Are used to determine the accuracy allowed for the solution when performing operations on numbers This will be further explained shortly

Rules for significant digits 1. Any digits from 1-9 are significant. Example: 436.433 m has 6 sig.digs. 2. Zeros between non-zeros are significant Example: 3004 g has 4 sig. digs

3. Zeros to the right of non zeros are significant, if there is a decimal point showing. Example: 45.00 cm has 4 sig. digs. 45200. km has 5 sig. digs. 4520000 km has 3 sig. digs note: the zeroes are place holders and must be written, but they do not imply accuracy in the number.

4. Zeros on the left are not significant Example: 0.000043 kg has 2 sig. digs. In this example, the leading zeros are not significant, because the measurement can also be made in another unit, in this case, 43 mg which also has 2 sig. digs. (A number cannot be made more accurate by changing its units. 5. All of the digits in the base of a number written in scientific notation are significant. Example: 6.02x1023 kg - 3 sig. figs

Determine the number of Sig Determine the number of Sig. Figs for each of the following, and tell why: a. 500 m b. 2.32 cm c. 4.3200 mg d. 0.00001 m e. 1500.0 kg f. 1 000 000 km g. 2.0000001 mm

From last day … What are significant digits and why are they used? How many significant digits are in the following numbers? 4.5009 Mw 12.00000 kJ 4.3 x 105 m

Calculations using Sig. Digs. When Multiplying/Dividing Multiply the complete numbers together, then round your answer so that it has the same number of Sig. digs as the term with the fewest. This is known as the Certainty rule.

Example: Determine the area of the room

Rounding … In all calculations using measurements (which have a measure of uncertaintly), we have to round to the appropriate number of significant digits. Do not round until the final answer! -remember that if the next digit is 5 or more, you round up, less than 5, down.

Perform the following calculations: a. 12m x 1m b. 10 cm x 1.3g/cm c. 24.3 cm / 8 cm d. 200 x 20

When Adding/Subtracting . Round your final answer off so that it has the same number of places after the decimal as the term with the fewest. (Don't use sig. digs at all) This is known as the precision rule.

Example: What is the perimeter of the room seen before?

Try these … 3.5 cm + 12.004 cm. 2000 g + 10.02 g 25 KJ – 12.5 KJ 460 m – 60 m 1500 a + 225 a 200 m/s2 + 1800 m 20 s2

Now complete the worksheet I gave you yesterday in class.

Review of yesterday… Round the following values to a certainty of 3 sig. digs. 15.64999 km 1600 m/s 4.5209 g 2.3334 x 105 g

2. Perform the following calculations, expressing your answer with the correct number of sig. figs. Cancel units where appropriate a. 25 m/s x 14.68 s. b. 240 g/L x 150.5 L c. 63.2 km + 4 km d. 130kg – 1 kg e. 80 km/h x 1h/60 min. x 1 min/60s. X 1km/1000 m.

Review: Scientific notation Scientific notation is a way to express very large or very small numbers. It is writing the values as a number between 1 and 10, multiplied by an exponent, base 10. - we simply move the decimal point so that it is after one non-zero number, and multiply that number using base 10 with an exponent indicating how many places we moved and in which direction.

Examples … Write the following in scientific notation. 1. 23 000 m. 2. 14.8 cm 3. 0.000000001 g 4. 384.2 x 106 J 5. 1900 x 10-3 J 6. 1900. x 10-3 W 7. 0.00034 x 103 kJ

Converting Units Physics calculations often require converting from one unit to another. One way we can accomplish this by multiplying by conversion units, aka ... conversions factors:

Try these 1. How many seconds in … i. A day ii. A week iii. A year. 2. Mary-lou just turned 15 years old. For how many days has she been alive?

And these… Convert 16 days into weeks Convert 20 m/s into km/h. Convert 80 km/h into m/s.

Conversion factors can be combined to come up with a single factor that we can use… i. For converting km/h into m/s … ii. For converting m/s into km/h.

Review: The SI System Convert 132 cm = __________ m remember: King Henry dances (pause) down the country meadow. or use conversion factors … Convert 132 cm = __________ m 23 kg = __________ g 45 mm = _________ µm 2 MHz = __________ GHz 40 MB = _________ GB

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