# vce physics units 3&4 exam revision lecture vce physics units 3&4 presented by: alevine magila exam     Post on 01-Mar-2020

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• VCE Physics Units 3&4

Presented by: ALEVINE MAGILA

Exam Revision

Lecture

• • Introduction

• How do things move without contact?

• How are fields used to move

electrical energy?

• How fast can things go?

• How can waves explain the behavior

of light?

• How are light and matter similar?

• Final tips and tricks

• • Introduction

• How do things move without contact?

• How are fields used to move

electrical energy?

• How fast can things go?

• How can waves explain the behavior

of light?

• How are light and matter similar?

• Final tips and tricks

• So then what can I provide in this lecture?

• Detailed look at VCAA Exam structures and styles

• Explain hard ‘separator’ questions from VCAA

• Strategies to tackle hard questions

• General advice from a past student

If what you’re looking for is content and revision summaries, have a look at

the course notes or topic tests.

Today’s Lecture

4

• • Introduction

• How do things move without contact?

• How are fields used to move

electrical energy?

• How fast can things go?

• How can waves explain the behavior

of light?

• How are light and matter similar?

• Final tips and tricks

• Magnetic Field Vectors

6

2011 Physics Exam 2

• Magnetic Field Vectors

7

2011 Physics Exam 2

• Magnetic Field Vectors

8

2013 Physics Exam

• Satellite Motion

9

2013 Physics Exam

• Astronauts in orbit only have one force acting on them: the weight force.

Therefore,

Σ𝐹 = 𝐹𝑔

Σ𝐹 = 𝐺𝑀𝑚

𝑅2 = 𝐹𝑔

SATELLITE MOTION

10

In year 12, we model satellite motion as uniform circular motion. We can account

for this in our equations:

Σ𝐹 = 𝑚𝑣2

𝑅 = 𝐺𝑀𝑚

𝑅2 = 𝐹𝑔

Σ𝐹 = 𝑚𝑣2

𝑅 = 4𝜋2𝑅

𝑇2 = 𝐺𝑀𝑚

𝑅2 = 𝐹𝑔

𝑎 = 𝑣2

𝑅 = 4𝜋2𝑅

𝑇2 = 𝐺𝑀

𝑅2 = 𝑔

• Satellite Motion

11

2013 Physics Exam

• DC Motors

12

2014 Physics Exam

• DC MOTORS

13

• DC Motors

14

2014 Physics Exam

• DC Motors

15

2014 Physics Exam

• Explanation Questions

16

The best advice I’ve heard when it

comes to explanation-style

questions?

Be specific, and answer the question.

• DC Motors

17

2014 Physics Exam

• Magnetic forces act on the coil create a torque.

• This torque causes the magnetic field to rotate

• DC Motors

18

2016 Physics Exam

• The magnetic forces acting on the coil are at a

maximum when the coil is at a flat, horizontal

position

• Therefore, a horizontal position if the best position

for the motor to start from rest

• Charged Particles Moving Through a

Magnetic Field

19

A moving charge in a magnetic field will experience a magnetic force. This

force can be calculated from the equation

𝐹 = 𝑞𝑣𝐵 From Newton’s second law, we know that whenever there is a net force, there

is an acceleration. Since there is a net magnetic force on a moving charge

through the magnetic field, it must be accelerating.

In reality, a moving charge does not change speed through a magnetic field –

it changes direction. Therefore, charged particles experience a centripetal

acceleration when they move through a magnetic field.

This yields the equation

𝑚𝑣2

𝑅 = 𝑞𝑣𝐵

The direction of the magnetic force on a charged particle can be calculated

using the right-hand slap rule, except this time, the thumb points in the

direction of the charge’s velocity instead of in the direction of the current.

If the charge is negative, the thumb points in the opposite direction to the

charge’s velocity.

• Particle Accelerators

20

• Weight Force/ Normal Force In

Satellites

21

2016 Physics Exam

• It is possible to experience weightlessness without being truly

weightless

• This occurs when the normal force acting on someone is 0 i.e

they are in freefall

• This gives them the sensation of being weightless, known as

apparent weightlessness

• Thus Emily is incorrect – it IS possible to FEEL weightless without

needing to be in deep space

• Graph of Gravitational Force vs

Distance

22

2002 Physics Exam

• There are approximately

13 squares

• Each square has a value

of 1000 x 3 x 106 = 3 x

109 J

• Therefore, the total energy

required equals 13 x 3 x

109 J

• • Introduction

• How do things move without contact?

• How are fields used to move

electrical energy?

• How fast can things go?

• How can waves explain the behavior

of light?

• How are light and matter similar?

• Final tips and tricks

24

2015 Physics Exam

• Induced EMF

25

2011 Physics Exam 2

• Transformers

26

2014 Physics Exam

• Making calculations about an electrical generator (such as calculating the

average power it produces) can be tricky because induced EMF is always

varying.

To compensate for this, physicists sometimes like to use a quantity called

the root mean square or RMS voltage.

This is the DC voltage it would take to produce the same average power as

an oscillating AC voltage.

To find the RMS voltage, we use the formula

𝑉𝑅𝑀𝑆 = 𝑉𝑝

2

𝑉𝑝𝑒𝑎𝑘 is the ‘peak’ voltage or the maximum voltage induced (this can be

read from a graph or an oscilloscope).

PEAK VOLTAGE AND RMS VOLTAGE

27

• Transmission of Electricity

28

• Transmission of Electricity

29

• Transformers significantly increases voltages to very high levels

• For a constant power, the voltage and the current are inversely

proportional (P = IV)

• An increase in voltage causes a decrease in current

• Decreasing the current decreases the power loss (𝑃𝑙𝑜𝑠𝑠 = 𝐼 2𝑅),

thereby reducing transmission losses

• • Introduction

• How do things move without contact?

• How are fields used to move

electrical energy?

• How fast can things go?

• How can waves explain the behavior

of light?

• How are light and matter similar?

• Final tips and tricks

• Pulley Questions

31

• Pulley Questions

32

• Banked Tracks

33

• When working through banked track problems, here are some

useful tips when through these types of questions:

• Draw a diagram (if one isn’t already supplied to you)

• Draw a force triangle. Again, the only forces acting on the

car that is moving at the design speed should be the weight

force and the normal force

• Note that for many questions, you won’t actually need the

mass of the car to find the answer

Tackling Banked Track Problems

34

• Vertical Circular Motion

35

• Length Contraction

39

• Muons

40

• Muons

41

• Why did the experiments

observe more muons

than expected?

• Because the half-life of

the muons, relative to the

experimenters, increased.

• This led to a higher

number of muons

reaching the detector

without decaying

• • Introduction

• How do things move without contact?

• How are fields used to move

electrical energy?

• How fast can things go?

• How can waves explain the behavior

of light?

• How are light and matter similar?

• Final tips and tricks

• The Doppler Effect

43

Emily is waiting to cross the road when an ambulance swerves around the corner with its sirens blaring. When the ambulance rushes towards Emily, the pitch of the siren seems to increase. As the ambulance passes Emily and drives into the distance, the pitch of the siren seems to decrease. Explain this effect.

• The change in pitch of the siren

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