Physics Predictions/Thoughts (3 Viewers)

[help2024]

Band 5 cut off?

 

[wizzkids]

Regarding 2024 HSC Physics Question 19 I just finished analysing the second proton, and if it stays within the chamber, then its motion will be an ellipse. The best answer is (C).

 

[Pielavender1234]

how screwed am i if i got 69 raw

 

[shoulfer]

how screwed am i if i got 69 raw

probs a decent b5

 

[Pielavender1234]

how that alignment is good, would this years exam be considered difficult?

 

[wizzkids]

Question 32. Analyse the evidence from at least three such experiments about the interaction between light and matter.
The examiners have made this question way harder than they imagined. If a scientist did not do experiments, then their work should not be mentioned. For example, Einstein did not do experiments on the interaction of light with matter. He analysed the experiments of other scientists. For example, most of Einstein's ground-breaking work on the photoelectric effect relied on the experiments of Philipp Lenard. It was Lenard who gathered all the data, which then Einstein interpreted in a new way, but Einstein didn't do the experiments. The trouble is, none of these scientists (apart from Newton) appear in the HSC syllabus.
Here is my list of top experiments involving light and matter:
(1) Isaac Newton - showed that white light could be split by a prism, and that if the colours were re-combined you could re-create white light.
(2) Francesco Grimaldi - discovered that when light passed through two narrow apertures, that the light spread out after the second aperture, a phenomenon he called "diffraction" and he correctly deduced that the light was bending around the aperture, and this indicated light was a wave.
(3) Rasmus Bartholin - discovered that light was split into two refracted rays when it passed through Iceland Spar (calcite crystals). The crystal has not one, but two refractive indices, so light has two velocities and two polarization axes when it passes through Iceland Spar. This discovery allowed scientists a convenient way to experiment with polarized light and make many new discoveries.
(4) Jean Foucault - measured the speed of light in water, showed that it was slower than the speed of light in air, and thereby disproved Newton's corpuscular theory of light.
(5) Joseph Fraunhofer - discovered dark absorption bands in the spectrum of the Sun, hypothesised that there were new elements.
(6) Gustav Kirchhoff - discovered that hot elements gave off a line spectrum, constructed the first spectroscope and then discovered dozens of new elements by spectroscopy. Also analysed the blackbody heat radiation spectrum.
(7) Philipp Lenard - showed that photoelectrons displayed a cut-off frequency for emission that depended on the identity of the metallic surface. Showed that the kinetic energy of photoelectrons was not increased by increasing the intensity of light, only by reducing the wavelength (or increasing the frequency) of the light.

 

[FudiddidoAdrian]

probs a decent b5

Damn rlly u normally so strict with alignment so imma trust you

 

[AKLAPRAY98]

dang i did kinda bomboclat icl -18 alr i thought i got -1 initially lol

 

[hughjanus_]

For question 20 - if C is correct, wouldn’t that also imply that B is correct? Also, despite the fact that Z is travelling faster than X from an external frame of reference, from the inertial frame of reference of X, Z appears to be stationary. Wouldn’t this mean X and Z tick at the same speed?

Interested to hear everyone’s thoughts, as my cohort was quite sure it was B.

 

[c4m3r0n]

Does anyone know the solution to 29b? Different masses seems obvious but the question specifically states that mass is negligible.

 

[hughjanus_]

Does anyone know the solution to 29b? Different masses seems obvious but the question specifically states that mass is negligible.

this tripped me up too - the mass of the wires is negligible, not the mass of the rods

 

[nonya2000]

Nope it said the mass of the wires are negligable

 

[nonya2000]

Can someone explain its not B?

 

[nonya2000]

here is explanation for 15
View attachment 45779

lol i used the right hand rule but didnt think it was called induced emf because i thought it only occured with change in flux

 

[nonya2000]

Please someone explain to me why question 18 isnt B

 

[nonya2000]

this looks like a fun paper, more interesting questions than some other hsc

Nope it was just essays besides the electron gun question.

 

[nonya2000]

this one
View attachment 45813

I saw that one, I still don't get it cause with B it makes a north pole which increases as current increases. I hope its B

 

[uart]

Why cant 20 be B

For question 20 - if C is correct, wouldn’t that also imply that B is correct?

That's a fair criticism, 20-B is certainly a correct statement. It just doesn't give as good a comparison of time dilatation effects for all three clocks as does 20-C. So 20-C will definitely be the accepted answer.

Also, despite the fact that Z is travelling faster than X from an external frame of reference, from the inertial frame of reference of X, Z appears to be stationary. Wouldn’t this mean X and Z tick at the same speed? Interested to hear everyone’s thoughts, as my cohort was quite sure it was B.

That's taking the inertial reference frame approximation way too far unfortunately. The question says to "assume that the satellites are inertial ref frames" just so we know that it's valid to apply the usual SR time dilation formula. You can't entirely ignore the system rotation (like assuming the Earth is non rotating and that the GS satellite is just hovering up there in space) - Which is essentially what you're doing with that statement.

 

[uart]

What was the one with the uniform and radial gravitational fields

Q31, compare the maximum height reached by a vertically launched projectile under the two different assumptions.

Assumption A - constant (uniform) gravitational field. g=9.8 m/s^2 and potential energy U = mgh.

Assumption B - (downward) gravitational acceleration is


and potential energy is


Qualitative answer.
g is just the point value of GM/r^2 at the Earth's surface (r = 6380x10^3 m), but an over estimate for higher elevations. This means that assumption A will generally under estimate the maximum elevation, as it over estimates the strength of the gravitational field at higher elevations.

Quantitative answer.
Equate changes in PE (U) to the initial KE, to obtain a formula for the max height under each assumption.

A :


B:


Not really sure how much of a quntatitve answer they will want here? The equation for B is a bit unwieldy, it can be algebraically simplified a little bit more, but still not easy to tell by cursory inspection that it's even an approximation to the equation of A (well technically A is an approx of B). If you sub in some numbers however then you'll see they are a close approximation. For u<100 m/s the maximum height reached will be very similar for both. At u>1000 m/s however, you'll notice some significant under estimates in equation A.

 

[baulkobruhmoment]

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