IB Physics

Folders, text books, calculators

• Paper 1 (Multiple Choice)

• Paper 2 (Extended response- some choice)

• Paper 3 (Options)

• Coursework SL-40 hours HL-60 hours

Let’s have a ball!

Topic 1 – Physics and physical measurement

Use the syllabus particularly when

studying for examinations

Ranges of sizes, masses and times

Order of magnitude

We can express small and large numbers using exponential notation

The number of atoms in 12g of carbon is approximately

600000000000000000000000

This can be written as 6 x 1023

Order of magnitude

We can say to the nearest order of magnitude that the number of atoms in 12g of carbon is 1024

(6 x 1023 is 1 x 1024 to one significant figure)

Small numbers

Similarly the length of a virus is 2.3 x 10-8 m. We can say to the nearest order of magnitude the length of a virus is 10-8 m.

Ranges of sizes, masses and times

You need to have an idea of the ranges of sizes, masses and times that occur in the universe.

Size

On your paper can you write in order of decreasing size the names of 5 very small things.

Size

Which is the smallest? What size is it to the nearest order of magnitude?

Size

The smallest objects that you need to consider in IB physics are subatomic particles (protons and neutrons).

These have a size (to the nearest order of magnitude) of 10-15 m.

Size

On your paper can you write in order of increasing size the names of 5 very large things.

Size

Which is the largest? How large is it to the nearest order of magnitude?

Size

The largest object that you need to consider in IB physics is the Universe.

The Universe has a size (to the nearest order of magnitude) of 1025 m.

Mass

On your paper can you estimate the masses of the 5 smallest objects you wrote down earlier.

Mass

What do you think the mass of the electron is?

10-30 kg!(0.000000000000000000000000000001 kg)

Mass

We have already decided that the Universe is the largest object. What do you think its mass is?

1050 kg

(100000000000000000000000000000000000000000000000000 kg)

Time

Now think of 5 small time intervals

(For example, the time it takes sound to travel 1 metre is a small time interval. Can you think of smaller?)

Time

Can you add order of magnitude estimates for your time intervals?

(For example, the time it takes sound to travel 1 metre is 10-3 seconds to the nearest order of magnitude)

Time

The smallest time interval you need to know is the time it takes light to travel across a nucleus.

Can you estimate it?

10-23 seconds

Time

What’s the longest time interval you can think of?

Time

The age of the universe.

Any ideas?

Time

The age of the universe.

1018 seconds

Copy please!

Size10-15 m to 1025 m (subatomic particles to the

extent of the visible universe)Mass

10-30 kg to 1050 kg (electron to the mass of the Universe)

Time10-23 s to 1018 s (time for light to cross a

nucleus to the age of the Universe)

A common ratio – Learn this!

Hydrogen atom ≈ 10-10 m

Proton ≈ 10-15 m

Ratio of diameter of a hydrogen atom to its nucleus

= 10-10/10-15 = 105

Estimation

For IB you have to be able to make order of magnitude estimates.

Estimation/Guess

What’s the difference?

Estimate the following:

1. The mass of an apple

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple

2. The number of times a human heart beats in a lifetime.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple

2. The number of times a human heart beats in a lifetime.

3. The speed a cockroach can run.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple

2. The number of times a human heart beats in a lifetime.

3. The speed a cockroach can run.

4. The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple

2. The number of times a human heart beats in a lifetime.

3. The speed a cockroach can run.

4. The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

5. The number of classrooms full of tea Mr Porter will drink in his lifetime.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple 10-1 kg

2. The number of times a human heart beats in a lifetime.

3. The speed a cockroach can run.

4. The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

5. The number of classrooms full of tea Mr Porter will drink in his lifetime.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple 10-1 kg

2. The number of times a human heart beats in a lifetime. 70x60x24x365x70=109

3. The speed a cockroach can run.

4. The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

5. The number of classrooms full of tea Mr Porter will drink in his lifetime.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple 10-1 kg

2. The number of times a human heart beats in a lifetime. 70x60x24x365x70=109

3. The speed a cockroach can run. 100 m/s

4. The number of times the earth will fit into the sun (Rs = 6.96 x 108, Re = 6.35 x 106)

5. The number of classrooms full of tea Mr Porter will drink in his lifetime.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple 10-1 kg

2. The number of times a human heart beats in a lifetime. 70x60x24x365x70=109

3. The speed a cockroach can run. 100 m/s

4. The number of times the earth will fit into the sun (6.96 x 108)3/(6.35 x 106)3 = 106

5. The number of classrooms full of tea Mr Porter will drink in his lifetime.

(to the nearest order of magnitude)

Estimate the following:

1. The mass of an apple 10-1 kg

2. The number of times a human heart beats in a lifetime. 70x60x24x365x70=109

3. The speed a cockroach can run. 100 m/s

4. The number of times the earth will fit into the sun (6.96 x 108)3/(6.35 x 106)3 = 106

5. The number of classrooms full of tea Mr Porter will drink in his lifetime.

(to the nearest order of magnitude)

Let’s do some more estimating!