Hi guys,
I'm doing the paper for my students, so I'm going to update this post as I go through it. So far I've finished the motion section, so you'll find the answers for this section below.
Please note I'm watching TV and eating at the same time and I'm human, so there could most definitely be mistakes. In fact, considering the size of this exam, I'd be surprised if I didn't make mistakes. If you think there's a mistake, just tell me and I'll fix it. I haven't showed working for the calculation questions, but if you'd like working for a particular question just ask.
Motion1a. 5 m s
-11b.
E
k initial = 128 J
E
k final = 108 J
Therefore, the collision is inelastic
1c. 40 N s to the left
2a. 2 m s
-22b. 8 N
3a. The arrow should be from the car to the centre of the circle; it should be labelled 'F
R'
3b. 38 N
4a.
- F
track on car or F
normal perpendicular to the track and outwards
- F
Earth on car or F
weight of car directly down the page
- F
R represented by a horizontal line to the left of the page
4b. 16.7
o5a. 20 m
5b. 24.82 m (the answer is not 25 m)
6a. 16 J
6b. 16 J (I disagree that signs would be needed in 6a and 6b, especially since 6b did not ask for a
change in energy)
6c. 2 m s
-16d. C
I'm not sure how they want you to explain this. I just wrote: 'The velocity is increasing from 0 to 0.4 m and decreasing from 0.4 to 0.8 m'
7a. 3.69 x 10
4 s
7b. 1.09 x 10
8 m
7c. Although the astronaut has a mass and is within a gravitational field and therefore has a weight, there is no normal reaction on the astronaut (i.e. they are in free fall). Since the astronaut's sensation of weight is determined by the normal reaction and there is no normal, they would feel weightless.
Electronics and photonics8a. You should have one resistor in series, and then two in parallel with one another
8b. The voltage drop across R
1 = 6 V, and the voltage drop across both R
2 and R
3 = 3 V
9a. LED; the LED emits light with an intensity that replicates the amplitude variation of the current through it
9b. Photodiode; it causes the amplitude of the current through it to replicate the changes in light intensity from the LED
10a. 15 kilo-ohms
10b. 75 kilo-ohms
11a. 50
11b. Firstly, negative values in the output signal correspond to positive values in the input signal because the amplifier is an inverting one. Secondly, the peaks of the output signal are flattened at +/-8 V because the input signal goes beyond +/-160 mV and the amplifier cannot give the maximum gain beyond this input range.
11c.
- Firstly, the sloped region of the characteristic should have a negative gradient
- The sloped region should end at -160 mV/+8 V and at +160 mV/-8 V
- Your x-axis should be in mV and your y-axis in V
Electric power12a. 3.2 x 10
-3 N upwards
12b. B
12c. 0.256 mV
12d. The student should replace the split-ring commutator with slip rings. Unlike a split-ring commutator, slip rings maintain fixed connections between the coil and the external circuit and therefore do not reverse the direction of the induced current.
13a.
- Between P and Q the flux should be zero
- Between Q and R the flux should:
- increase at a steady rate
- then remain constant
- Between R and T the flux should:
- decrease back to zero steadily over the same rate at which it initially increased
- then remain at zero
13b.
- Between P and Q the emf should be zero
- Between Q and R the emf should:
- instantly rise/drop to a constant value for the same amount of time the flux was increasing
- then drop back to zero when the flux remains constant
- Between R and T the emf should:
- instantly drop/rise to a constant value for the same amount of time the flux is decreasing
- then should go back to and remain at zero
13c. As the loop enters the field, there is an increase in flux through the loop into the page (when viewed from Figure 14b). Lenz's law states that the induced field will oppose this change in flux, meaning the induced field will be out of the page. With the induced field in this direction, the induced current must flow
through the ammeter from X to Y.
14a. 25 Hz
14b. 9.55 x 10
3 V
15.
- There should be one horizontal line through the solenoid with an arrow pointing to the right
- Four lines should loop around the solenoid with arrows pointing to the left
- None of the lines should be touching
16a. 2 A
16b. 10 V
16c. 16 W
16d. 0.2 A
16e. 0.16 W
16f. This model represents how electricity is transmitted from power stations to houses. Since the power demands would be constant and since P = VI, increasing the transmission voltage would reduce the transmission current. Reducing the transmission current reduces power losses, since P
loss = I
2R. Specifically in terms of Alan and Becky's model, increasing the transmission voltage by a factor of 10 reduces the transmission current by a factor of 10, which reduces the power losses by a factor of 100.
Light and matter17a. When the slide is put in place, this point will be a bright band. This is because, at this point, the light from each slit travels the same distance (i.e. the path difference is zero) and therefore constructively interferes at this point.
17b. C
18a. 5 x 10
14 Hz (seriously VCAA?)
18b. h = 4 x 10
-15 eV (I imagine some variation would be allowed here)
18c. Your graph should be straight over the top of the dotted graph
18d. Your graph should:
- intercept the x-axis at 7.5 x 10
14 Hz
- have the same gradient as the dotted line
19a.
E
n = 2 = 91.91 eV
E
n = 3 = 108.88 eV
19b. You should have drawn a line
downwards from the n = 3 line to the n = 2 line
20a. The photoelectric effect supports light behaving as particles. This effect shows that the energy of light is dependent on frequency and independent of intensity. The particle model correctly predicts these two outcomes while the wave model does not.
20b. When accelerated through an atomic lattice, electrons produce a diffraction pattern. This indicates that electrons must have a wavelength, which is a wave property.
*Keep in mind questions 20a and 20b were only worth 2 marks each*
21a. Electrons have a wavelength. They can only orbit atoms such that their wavelength is a whole number multiple of the orbit's circumference, because otherwise a standing wave will not occur. As electrons can have only particular wavelengths to orbit atoms, they can also have only particular energies.
21b. You should draw two diagrams: one where an electron is orbiting such that its wavelength fits in a whole number of times without overlap, and one where an electron is orbiting such that its wavelength does not fit in a whole number of times with overlap. I imagine you would be expected to annotate each diagram, indicating how the former is a stable, standing wave pattern while the latter will result in destructive interference.
*In regards to question 21, I'm really not sure how the marks will be allocated*
22. 7.29 x 10
7 m s
-1Detailed study: Sound1. B 2. C 3. B 4. B 5. A 6. C 7. B 8. D 9. D 10. B 11. D (B?)
Materials - courtesy of ashmitch!
1. A 2. A 3. C 4. B 5. B 6. D 7. B 8. C 9. D 10. C 11. D
HOPE THIS HAS BEEN HELPFUL
And thank you everyone for your input!
EDIT: Note that some changes have be made this morning, specifically to questions 16f and 20b.
I would appreciate some more advice on questions 10 and 11 of sound. There's been very mixed responses to question 10, but for question 11 it seems the answer is D.
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