1.36

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1.36

15 March 2012

10:27
· 1.36 understand that:
· the universe is a large collection of billions of galaxies
· a galaxy is a large collection of billions of stars
· our solar system is in the Milky Way galaxy
[cid:image001.png@01CD0B2F.897AFE80]

Comparative sizes of planets and stars

[cid:image002.jpg@01CD0B2F.897AFE80]

Comparative sizes of galaxies

[cid:image003.png@01CD0B2F.897AFE80]

Powers of 10 - Cosmic Voyage

[cid:image004.png@01CD0B2F.897AFE80]

1.36 Space is big! Scale model of the solar system

12 May 2011

14:47
· Type the length of your classroom into cell B5 to get the solar system scaled to fit!
· Check out column U for information about the nearest star to our solar system!

>

Online version

http://www.exploratorium.edu/ronh/solar_system/

1.36 Plenary Answers

15 March 2012

10:30
1. What is the solar system?

Everything that orbits our local star, the Sun
2. What is the Milky Way?

The galaxy that contains our solar system
3. What is a galaxy?

A huge collection of billions of stars
4. How many galaxies are there in the Universe?

Billions

scale model.xls Download this file

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1.35

________________________________________

1.35

15 March 2012

10:26
• 1.35 use the relationship between orbital speed, orbital radius and time period:

orbital speed = 2×Π×orbital radius

time period

v = 2×Π×r

T

v = 2×Π×r

T

v = orbital speed (m/s or km/hr)

r = orbital radius (m or km)

T = orbital period (s or hr)

1.35 Plenary Answers

15 March 2012

10:30

Pearson Answers, p.56, Q3+4

[cid:image001.png@01CD0B2F.985729B0]

[cid:image002.png@01CD0B2F.985729B0]

[cid:image003.png@01CD0B2F.985729B0]

[cid:image004.jpg@01CD0B2F.985729B0]

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1.33

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1.33

15 March 2012

10:25
· 1.33 explain that gravitational force
· causes moons to orbit planets
· causes the planets to orbit the sun
· causes artificial satellites to orbit the Earth
· causes comets to orbit the sun
>

http://phet.colorado.edu/en/simulation/gravity-and-orbits

1. Turn on

[cid:image001.png@01CD0B2F.820FE2A0]
2. Experiment with the 4 different situations to see what orbits what and why

[cid:image002.png@01CD0B2F.820FE2A0]
3. Still not sure? Try

[cid:image003.png@01CD0B2F.820FE2A0]

PhET animation - gravity and orbits

31 January 2012

13:34
>

Website

http://phet.colorado.edu/en/simulation/gravity-and-orbits

Embed code for your blog

Click to Run

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1.32 and 1.34

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1.32 and 1.34 Starter

16 March 2012

10:18

Tell the person next to you…
· the names of the 8 planets in our solar system (in order!)

Answers
1. Mercury (closest to the sun)
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune (furthest from the sun)

How can you remember this?
· "My Very Educated Mother Just Served Us Nothing"
· "My Very Easy Method Just Speeds Up Naming (Planets)"

[cid:image001.jpg@01CD0B2F.7607BF00]

1.32 and 1.34 Starter 2 - Quick Planets quiz

12 May 2011

15:52
>

1.32 and 1.34 Investigating the solar system - answers

16 March 2012

10:26

Moons
1. How are moons different from planets?

Planets orbit the Sun; moons orbit planets
2. The Earth has one moon. Do all planets?

No. Mercury and Venus have no moon, Mars has 2 and Venus and Saturn both have over 60 each!
3. Do moons have gravitational fields?

Yes, any body that has mass generates a gravitational field. The gravitational field strength on our Moon is

1.62N/kg, which is about 1/6 of the gravitational field strength on Earth.

Gravitational fields
4. Which planet has the largest gravitational field? What is it?

Jupiter = 26N/kg
5. Which planet has the smallest gravitational field? What is it?

Mercury = 4N/kg (Pluto doesn't count! See Q.11)
6. What is the relationship between the mass of the planet and the gravitational field strength of the planet?

The larger the mass of a planet, the stronger the gravitational field strength

Period of orbit
7. Which planet has the shortest period of orbit? What is it?

Mercury = 3 x Earth month = 0.25 x Earth year

(if you lived on Mercury you would be over 60 years old!)
8. Which planet has the longest period of orbit? What is it?

Neptune = 1978 x Earth month = 164 x Earth year

(if you lived on Neptune you would be 0.1 years old!)
9. What is the relationship between the period of orbit of a planet and its distance from the Sun?

The larger the distance from the Sun, the greater the period of orbit
10. What is the relationship between the surface temperature of a planet and its distance from the Sun?

The larger the distance from the Sun, the lower the surface temperature

(the one exception to this rule is Venus which has an exceptionally high surface temperature of +465oC due to an atmosphere of 96% CO2 and clouds of H2SO4!)

Classification of astronomical bodies
11. What 2 classifications are the planets grouped into? What are the key features of each group?

4 Inner "rocky" planets
o Rocky
o Smaller diameters
o Shorter periods

4 Outer "gas giant" planets
o Gaseous
o Larger diameters
o Longer periods
o Have rings (most noticeable for Saturn, but they all have them)
o What are 2 key features of comets and 3 key features of their orbits?
i. Made from ice and dust
ii. Have a tail when they pass close to the Sun
i. Highly elliptical orbit - see blue trace.

[cid:image002.jpg@01CD0B2F.7607BF00]
o Sometimes pass close to the Sun at very high speeds but spend most of their orbit in the outer reaches of the solar system moving at much lower speeds
iii. Periods can be from a few years to hundreds of thousands of years
13. How do the orbits of asteroids differ from the orbits of comets?

Asteroids are lumps of rock that mostly orbit the Sun in the "Asteroid Belt", between Mars and Jupiter, in approximately circular orbits
14. Which planet in the animation is no longer a planet? (it has been reclassified as a planetoid or dwarf planet)

Pluto was reclassified as a planetoid or dwarf in 2006 for reasons including its highly elliptical and tilted orbit

PhET animation - my solar system

31 January 2012

13:34
>

Website

http://phet.colorado.edu/en/simulation/my-solar-system

Embed code for your blog

planets quiz.swf Download this file

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1.24

________________________________________

1.24 starter

14 March 2012

16:55
>
· Can you explain this in terms of the Principle of Conservation of Momentum?

1.24

Tuesday, July 06, 2010

3:04 PM
· 1.24 demonstrate an understanding of Newton’s third law
[cid:image001.png@01CD05AD.22C158B0]
>
>

Newton's 1,2,3 summary.swf Download this file

N3 pairs.swf Download this file

N3 guy jumps off boat.swf Download this file

1.23 Plenary answers

1.23

________________________________________

1.23 starter

14 March 2012

16:23
· Why does kicking a brick hurt your foot?
· Why does kicking a football not hurt your foot?
>

1.23

Tuesday, July 06, 2010

3:04 PM
· 1.23 use the relationship between force, change in momentum and time taken:

force = change in momentum

time taken

F = Δp / t

From N2L F = m x a

but a = v - u / t

so F = m (v - u) / t

F = mv - mu / t

but p = mv

so F = pf - pi / t

F = Δp / t

can be written as Δp = F x t = Impulse

We can express the green equation in words as...

"Force is the rate of change of momentum"

How to catch a high velocity egg!

Example 1

Why would you prefer to fall onto a bed than onto concrete? (3 marks)

Answer
· Concrete or soft bed, your change in momentum is equal
· With a soft bed, this change in momentum takes place over a longer time
· This means that the force needed to change your momentum is less

or use the equation
· Impulse = Δp = F x t where Δp = constant
· soft bed => increases t
· and therefore decreases F

Example 2 - Pearson, p.41

[cid:image001.jpg@01CD05A9.D9A789E0]

Answer

F = Δp / t

10,000 = Δp / 60

Δp = 600,000kgm/s

Δp = mv - mu

Δp = m(v - u)

600,000 = 1,200(v - 2000)

v - 2000 = 500

v = 2500m/s

Impulse - kicking a ball and kicking a brick.swf Download this file

1.21

________________________________________

1.21

Tuesday, July 06, 2010

3:04 PM
· 1.21 use the ideas of momentum to explain safety features
[cid:image001.png@01CD05AD.1B326120]

Example

Explain how motorcycle and bicycle helmets can protect their users during a collision

Answer
· Helmet or bare head, the change in momentum of your head during a collision is equal
· With a helmet, this change in momentum takes place over a longer time
· This means that the force needed to change the momentum of your head is less

or use the equation
· Impulse = Δp = F x t where Δp = constant
· cushioning in helmet => increases t
· and therefore decreases F

1.21 Plenary answers

13 March 2012

15:20

Physics for You p.147 Q2c

2c. Why is the front of a car designed to collapse in a serious collision? (3 marks)

· There is a force when you crash that decelerates the car (decreases your momentum)
· If the front of the car collapses (this is the crumple zone), this force acts for a longer time than if the front of the car were rigid
· This means that the force needed to change the car's momentum is less and there's less risk of injury to the driver

or use the equation
· Impulse = Δp = F x t where Δp = constant
· crumple zone increases t
· and therefore decreases F

1.20 to 1.24 Plenary answers

________________________________________

1.20 to 1.24 Plenary quick+easy questions and answers

29 September 2010

13:54
>

1.20 to 1.24 Plenary extension question

13 March 2012

15:20

Physics for You p.147 Q6

[cid:image001.png@01CD05AF.277754C0]

6.

Consider initial momentum

Man

p = m x v

p = 80 x 0

p = 0kgm/s

Bullet

p = m x v

p = 0.02 x 400

p = 8kgm/s

total initial momentum = 8+0 = 8kgm/s

Principle of Conservation of Momentum tells us:

total initial momentum = total final momentum

Σpi = Σpf

so total final momentum = 8kgm/s

Consider final momentum

Σpf = pbullet + pman

8 = 0 + pman

pman = 8kgm/s

Man

p = m x v

8 = 80 x v

v = 0.1m/s

· Considerably less dramatic than Hollywood!

Momentum and Impulse Plenary (Gapfill) - PFY.ppt Download this file

1.22

________________________________________

1.22

Tuesday, July 06, 2010

3:04 PM
· 1.22 use the conservation of momentum to calculate the mass, velocity or momentum of objects

Momentum conserved in collisions

>

and 1.20 animation

Momentum conserved in explosions

>

>

Example - Pearson, p.41

[cid:image001.jpg@01CD0351.148D95F0]

Consider final momentum

Truck, plasticine and pellet

p = m x v

p = (0.1+0.002) x 0.8

p = 0.0816kgm/s

total final momentum = pf = 0.0816kgm/s

Principle of Conservation of Momentum tells us:

total initial momentum = total final momentum

Σpi = Σpf

so total initial momentum = pi = 0.0816kgm/s

Consider initial momentum

Truck and plasticine

p = m x v

p = 0.1 x 0

p = 0kgm/s

Pellet

p = m x v

0.0816 = 0.002 x v

v = 40.8m/s

1.22 animation

14 March 2012

15:49

Website:

http://www.walter-fendt.de/ph14e/collision.htm

Embed code for your blog:

Example:

http://maddog11physics.posterous.com/conservation-of-momentum-animation#

newtons_cradle[1].swf Download this file

AirTrack simulation.swf Download this file

1.22 Plenary questions

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1.20

________________________________________

1.20

Tuesday, July 06, 2010

3:04 PM
· 1.20 recall and use the relationship between momentum, mass and velocity:

momentum = mass × velocity

p = m × v

p = m × v

p = momentum (kgm/s)

m = mass (kg)

v = velocity (m/s)

Investigating Momentum

________________________________________

Starter - Spot the mistakes!

13 March 2012

16:35
· http://sites.google.com/site/winfailphysics/all-videos/roadrunner-human-canno...
· http://sites.google.com/site/winfailphysics/all-videos/roadrunner-spring-punch
· You know that these situations are wrong, but why are they wrong?!

Guided discovery - Investigating Momentum

14 March 2012

07:20

When we collide two gliders on the

air track, what happens?

Situation 1: Elastic collision with a stationary glider

Initial

Initial speed of LH glider = ul = 1m/s

Initial speed of RH glider = ur = 0m/s

[cid:image001.jpg@01CD0350.F6AD6C40]

Final

Final speed of LH glider = vl = 0m/s

Final speed of RH glider = vr = 1m/s

[cid:image002.jpg@01CD0350.F6AD6C40]

We can represent this graphically as

Initial

[cid:image003.png@01CD0350.F6AD6C40]

Final

[cid:image004.png@01CD0350.F6AD6C40]

Conclusion
· It appears that the speed is "transferred" to the RH glider

Situation 2: Inelastic collision with a stationary glider

Initial

Initial speed of LH glider = ul = 1m/s

Initial speed of RH glider = ur = 0m/s

[cid:image005.jpg@01CD0350.F6AD6C40]

Final

Final speed of LH glider = vl = 0.5m/s

Final speed of RH glider = vr = 0.5m/s

[cid:image006.jpg@01CD0350.F6AD6C40]

We can represent this graphically as

Initial

[cid:image003.png@01CD0350.F6AD6C40]

Final

[cid:image007.png@01CD0350.F6AD6C40]

Conclusion
· Speed is conserved in the collision
· Total Initial speed = Total Final speed

Situation 3: Head on collision

Initial

Initial speed of LH glider = ul = 1m/s

Initial speed of RH glider = ur = -1m/s

[cid:image008.png@01CD0350.F6AD6C40]

Final

Final speed of LH glider = vl = 0m/s

Final speed of RH glider = vr = 0m/s

[cid:image009.png@01CD0350.F6AD6C40]

We can represent this graphically as

Initial

[cid:image010.png@01CD0350.F6AD6C40]

Final

[cid:image011.png@01CD0350.F6AD6C40]

Conclusion
· Velocity is conserved in the collision
· Total Initial velocity = Total Final velocity

Situation 4: Head on collision with different masses

Initial

Initial speed of LH glider = ul = 1m/s

Initial speed of RH glider = ur = -1m/s

[cid:image012.png@01CD0350.F6AD6C40]

Final

Final speed of LH glider = vl = 0m/s

Final speed of RH glider = vr = 0m/s

[cid:image013.png@01CD0350.F6AD6C40]

Problem!

Our previous conclusion that
o Velocity is conserved in the collision

doesn't hold for this situation!

Why do they move off to the left?

Because the RH glider has twice the mass

What could I change about the LH glider to make both gliders stop after the collision?
o Double the mass (obvious)
o Double the initial velocity

We can represent this graphically as

Initial

[cid:image014.png@01CD0350.F6AD6C40]

Final

[cid:image015.png@01CD0350.F6AD6C40]

So something is conserved in the collision, but what is it?

What does the area of the rectangles represent?!

Time to label our axes!

[cid:image016.png@01CD0350.F6AD6C40]

Final Conclusion
· The area of the rectangles are mass x velocity
· Momentum = mass x velocity
· So momentum is conserved in collisions

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7.19 and 7.20

________________________________________

7.19 and 7.20

12 January 2012

10:32
· 7.19 understand that a chain reaction can be set up if the neutrons produced by one fission strike other U-235 nuclei
· 7.20 understand the role played by the control rods and moderator when the fission process is used as an energy source to generate electricity
>
>
>
>

7.17 to 7.20 Plenary Answers

13 January 2012

14:17
1. What is the process of splitting large nuclei called?

Fission
2. How is 235U made to decay inside a nuclear reactor?

It is bombarded by a neutron to turn it into 236U which is unstable and rapidly decays

[cid:image001.png@01CD002A.AA619240]
3. What are the generic names for the products of a fission reaction?

Two daughter nuclei and either two or three neutrons are produced

[cid:image002.jpg@01CD002A.AA619240]
4. In what form is energy produced during a fission reaction?

Energy is released in the form of Kinetic Energy of the products of the reaction - the two daughter nuclei and the neutrons
5. For a stable chain reaction to occur how many neutrons must, on average, collide with another nucleus of 235U?

Exactly one. If the value is less than this the reaction will eventually finish. If the value is more than this the reaction will very rapidly accelerate to explosive rates - utilised in nuclear weapons

[cid:image003.jpg@01CD002A.AA619240]
6. What is the purpose of the moderator?

The moderator slows down the neutrons produced by fission so that they can be captured by other 235U nuclei and thus sustain the chain reaction
7. What do the control rods do?

Control rods absorb excess neutrons in the reactor and thereby provide a method for controlling the chain reaction

[cid:image004.jpg@01CD002A.AA619240]

7.17 and 7.18

________________________________________

7.17 and 7.18 starter

13 January 2012

14:02

A fuel that doesn’t burn. What is it?

Answers
· Uranium. When Uranium atoms split into two (fission) they release energy which can be captured in a nuclear power station. This is a nuclear reaction and is fundamentally different to burning (combustion is a chemical reaction)

7.17 and 7.18 starter 2

13 January 2012

14:02

How many protons and neutrons are there in
· 23592U?
· 23692U?

Answers
· 23592U = 92 protons; 143 neutrons.

This radioisotope of Uranium is commonly used as a fuel for nuclear power stations
· 23692U = 92 protons; 144 neutrons

This radioisotope of Uranium is highly unstable and is artificially created in nuclear power stations where it undergoes fission

7.17 and 7.18

12 January 2012

10:32
· 7.17 understand that a nucleus of U-235 can be split (the process of fission) by collision with a neutron, and that this process releases energy in the form of kinetic energy of the fission products
· 7.18 recall that the fission of U-235 produces two daughter nuclei and a small number of neutrons
>
>

PhET animation - nuclear fission

31 January 2012

13:34
>

Website

http://phet.colorado.edu/en/simulation/nuclear-fission

Embed code for your blog

Click to Run

U235 fission animation.swf Download this file

Nuclear Fission.pptm Download this file