2016 VCE exam guide — Physics: Bright ideas to help students excel
The Physics examination tests all of units 3 & 4 including Motion, Electronics, Electric Power and Light & Matter, and one Detailed Study.
Doing Physics exam-style questions is one of the best ways to study Physics.
Work through past VCAA and trial exams and identify the topic in a question.
If you don’t know how to answer a particular question, study the solution and add some points to your sheet of notes under the topic heading.
Motion
How do you do energy calculations?
For energy calculations it doesn’t matter where the zero of height is taken to be for GPE, however the zero of extension for SPE does matter and is always the unstretched length of the spring.
How do you best answer projectile motion questions?
Always use a vertical list of quantities (u, v, a, s and t) and a horizontal list and work out any missing quantities in these two directions.
Use the equations of motion but only for the quantities in one list at a time.
The time values would be the same in each list. To find the final velocity, use the ‘v’ values from each list in a right angle triangle and use pythag.
Where do the forces act in vertical circular motion?
In vertical circular motion, understand the direction of the forces at the top and the bottom for a car on a track, a mass on a string etc.
Weight is always DOWN and the net force is always TOWARDS THE CENTRE.
The third force: N (normal force) or T (string tension) must be joined head to tail with W to give the net force.
How does momentum work in collisions?
In a collision, one object will LOSE momentum and the other object will GAIN the same amount of momentum, meaning the total momentum is conserved.
How are weight and apparent weight different?
Since weight = m × g, true weightlessness (W = 0) is when g = 0. Likewise, apparent weight = N so apparent weightlessness is when N = 0.
Electronics
What ratios apply with voltage dividers?
Voltage drop across the resistors is in the same ratio as the resistances. If there is a 3000 Ω and a 1000 Ω then the voltages will be in a 3 : 1 ratio also.
Does clipping occur?
Determine peak output from the gain (e.g. 200) and peak input (e.g. ±30 mV). Invert if needed, then draw the full Vout graph (e.g. peaks of ±6 V). Determine max and min Vout (e.g. ±4 V) from the transfer characteristic and rub out above 4 V and below —4 V and replace with flat lines to show the clipping.
Electric Power
Which rule to use?
The right hand slap rule and the right hand grip rule have different applications. RH GRIP gives the magnetic field direction for a single wire or for a solenoid.
What is the direction of the induced current?
There are three steps to Lenz’s Law:
1. What flux change is occurring? (The flux might be reducing).
2. What would oppose this or restore the original? (Increase the flux).
3. Hence what is the current direction? (Use the RH grip rule).
What type of output does a generator give?
A generator works in the opposite way to a motor. As a generator spins, current is induced in the coil. This current flow will change direction every half-turn, so it is AC. Slip rings are used to harness the AC. If a DC output is required, the reversal must be cancelled out and a split ring commutator achieves this.
What gets ‘lost’ along transmission lines?
Voltage and power are both lost along transmission lines. Output voltage at the other end of the lines is input voltage minus the lost voltage. Output power is input power minus lost power. Remember to use the resistance of both power lines.
Light and Matter
How does the photoelectric effect work?
The photoelectric effect is an energy experiment.
The electrons in the metal need a minimum amount of energy to be ejected. From the energy of the incident light (E = h f), some is used to eject the electrons (equal to the work function) and any energy left over becomes the kinetic energy of the photoelectrons.
Different colours of light have different energies but different intensities of the same colour do not. Different metals have different minimum energies needed to eject the electrons.
How is the shape of an electron diffraction pattern determined?
The diffraction pattern is determined by wavelength and is similar to that from X-rays only if the de Broglie wavelength of the electron is similar to the wavelength of the X-rays.
Note that electrons do NOT have a frequency NOR do they travel at the same speed as the X-rays.
Craig Tilley has been a Physics examination assessor for more than 17 years and is the author of the A+ Physics Units 3 & 4 Exam Book, co-author of the A+ Physics Notes books and subject lead author of Heinemann Physics 12 4th Edition
EXAM DETAILS
PHYSICS
When: November 9, 9am-11.45am
Reading: 15 minutes
Writing: 2 and half hours
Worth: 60 per cent of study score