Name the units for the following quantities: Lesson link Name the units for the following quantities: Current Charge Velocity Distance Force Energy

Units, Quantities and Significant Figures 28/11/2018 c/w Units, Quantities and Significant Figures

Learning Objectives Developing Recall and use the SI units for physical quantities Securing Recall and use multiples and sub-multiples of units Exceeding Be able to convert different units and use significant figures

Engage Systeme Internationale Sounds fancy right? The systeme internationale is a list of the standard units that we should use in physics For example, we should measure distance in metres not in ‘kilometers’ or ‘parsecs’ or ‘cats in a row’ You are expected to learn all of the standard units. If something is given in a different unit, you simply convert it first Metre (for distance) Kilogram (for mass) Second (for time) Ampere (for current) Kelvin (for temperature) Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9

For example: the radius of the sun is 659700000m Engage Standard form Often, numbers are too big or too small to write out in full, even if you round to significant figures For example: the radius of the sun is 659700000m So what we do is use standard form. Standard form summarises the number into a form ending in ‘x10’ to a certain power. For example: 300,000 would be 3 x 105 0.006 would be 6 x 10-3 5689 would be 5.7 x 103 So, for large numbers look for the number of digits after the first digit and for small ones, the number of digits after the decimal place! Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9

Engage Standard form Complete the following sheets. Write your answers on the sheet and stick the sheet in your book Useful note: There is a ‘x10’ button on the bottom of most calculators (sometimes shown as ‘EXT’ Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9

Explore Orders of Magnitude Certain powers of 10 (e.g. x103) are known as orders of magnitude and are just easy ways of keeping the numbers in set categories that are easy to say. For instance, you’re used to the word kilometre, and that’s actually using the prefix ‘kilo’ which means 1000 (or x103) Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9 1 millilitre 1 litre 1 kilolitre

Explore Put these orders of magnitude in order from smallest to largest and link them to their power Giga (G) Kilo (K) Mega (M) Milli (m) pico (p) Micro (μ) Centi (c) Nano (n) Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9 10-12 10-9 10-6 10-3 10-2 103 106 109

Explore Copy out this list into your book and be very neat as you’ll need to refer back to it in future! 10-12 10-9 10-6 10-3 10-2 103 106 109 pico (p) Nano (n) Micro (μ) Milli (m) Centi (c) Kilo (K) Mega (M) Giga (G) Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9 Let’s consider the height of something, work in pairs to think of something that would have their height measured in each order of magnitude

10-12 10-9 10-6 10-3 10-2 103 106 109 pico (p) Nano (n) Micro (μ) Milli (m) Centi (c) Kilo (K) Mega (M) Giga (G)

Explore Converting orders of Magnitude Very frequently, physics exams will expect you to convert units. They won’t always tell you to do it, its up to you to see if the unit given isn’t the standard unit For instance, quite often you’ll be given mA instead of A for current. So you’ll need to convert it first! This is super easy, you just need to remember your order of magnitude value! So as you know that ‘milli’ means “x 10-3” then 15mA is 15x10-3A Have a go! Convert 45mA into A Convert 76GA into A Convert 25km into m Convert 12pN into N Convert 34nm into m Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9

Explore Significant Figures These are important as they can be the difference between the mark for a calculation. The word significant means: having meaning. With the number 368249, the 3 is the most significant digit, because it tells us that the number is 3 hundred thousand and something. It follows that the 6 is the next most significant, and so on.1 With the number 0.0000058763, the 5 is the most significant digit, because it tells us that the number is 5 millionths and something. The 8 is the next most significant, and so on. Pico -12 Nano -9 Micro -6 Milli-3 centi -2 Kilo 3 Mega 6 Giga 9

Explore Significant Figures We round off a number using a certain number of significant figures. The most common are 1, 2 or 3 significant figures. Remember the rules for rounding up are the same as before: “If the next number is 5 or more, we round up”.  0.00245 correct to 1 significant figure?  0.002  0.0355 correct to 1 significant figure? 0.04 Complete the sig figs sheet  0.0355 correct to 2 significant figures? 0.036  7.994 to two significant figures? 8.0

Learning Objectives Developing (3) Recall and use the SI units for physical quantities Securing (4-6) Recall and use multiples and sub-multiples of units Exceeding (7-9) Be able to convert different units and use significant figures

Complete all questions on all worksheets provided Independent Study Complete all questions on all worksheets provided