HSC Physics Question Thread

[Bubbly_bluey]

Hey! just a quick little question. When calculating gravitational potential energy, does the radius include the distance between the two centres of the planets or only the radius of one mass + the aplitude?

[liamwindeyer]

Hey! just a quick little question. When calculating gravitational potential energy, does the radius include the distance between the two centres of the planets or only the radius of one mass + the aplitude?

It would be the distance between the centres of the planets, like Newton's Universal Law of Gravitation formula 

Edit - Should've added that the GPE formula and Newton's formula are practically the same concept; used for different scenarios. GPE is usually used for when a smaller satellite is orbiting a planet, whilst Newton's is usually used for the effect of gravity between planets (or two similarly sized objects)

[smile123]

PLEASE HELP 

[jakesilove]

PLEASE HELP 

Hey! Let's use trigonometry to find the horizontal distance the pilot will need to fly before they crash. We know that the angle between the ground and the rising slope is 4.3 degrees. The height (therefore, the opposite side) will have a height of 35m. Draw yourself a diagram if this isn't clear, but we can use trigonometry to show that





Great! So, the pilot will be level with (and therefore hit) the ground in 465.49m. The pilot is travelling



Therefore





Poor pilot

[smile123]

thankyou for the help

[kiwiberry]

Why is it harder to turn a hand-powered generator attached to an electrical device than one connected to nothing? Does it have something to do with back emf?

[Abi21]

Hey Jake,

I am in year 10 and am currently choosing my VCE subjects. I have one spot left and I'm trying to choose between physics?chemistry. I noticed that you've done both subjects and i was wondering what are some of the pros of Physics and why should i choose it instead of chem. Sorry if this is a little irrelevant.

[TooLazy]

Hey Jake,

I am in year 10 and am currently choosing my VCE subjects. I have one spot left and I'm trying to choose between physics?chemistry. I noticed that you've done both subjects and i was wondering what are some of the pros of Physics and why should i choose it instead of chem. Sorry if this is a little irrelevant.

I find physics more interesting and easier, but chem for me is straight cancer

[Bubbly_bluey]

hello! i am having trouble understanding the equivalence between mass and energy, more specifically einstein's famous: e= mc².
when an object travels at 0.9c,its mass apparently gets converted into energy but what is that energy? does it get released somewhere?
Thanks for putting up with me

[jakesilove]

Why is it harder to turn a hand-powered generator attached to an electrical device than one connected to nothing? Does it have something to do with back emf?

Hey! When the device is connected to an electrical device, electricity is being removed from the system (ie. current is being drawn away to power that device). Thus, the person turning the generator has to add extra energy (kinetic to electrical) to make up for this net loss of energy in the system. So, the generator is harder to turn! Additionally, there may be eddy currents produced in the electrical device, which will also draw energy away.

Jake

[jakesilove]

Hey Jake,

I am in year 10 and am currently choosing my VCE subjects. I have one spot left and I'm trying to choose between physics?chemistry. I noticed that you've done both subjects and i was wondering what are some of the pros of Physics and why should i choose it instead of chem. Sorry if this is a little irrelevant.

Hey!

I personally prefer Physics. The concepts are broad and fundamental, and it contains a lot more mathematical operations. As a maths-head myself, the Maths surrounding Chemistry was a bit trivial. At the end of the day, it's all about what excites you more. Look at the curriculums briefly (I'm in NSW, so don't know what the VCE curriculum looks like) and see whether there is anything that interests you. Do you care more about space, or chemical reactions? Electricity, or processes that allow the human body to function? Think about what you've learned up until now, and whether you've enjoyed Chemistry more than Physics or vice versa.

Let me know if you have any more questions!

[jakesilove]

hello! i am having trouble understanding the equivalence between mass and energy, more specifically einstein's famous: e= mc².
when an object travels at 0.9c,its mass apparently gets converted into energy but what is that energy? does it get released somewhere?
Thanks for putting up with me

Hey! Really good question; my answer is that this goes way beyond the curriculum. In simple terms, when an object speeds up, it JUST gains energy. This energy comes in the form of kinetic energy. However, since E=mc^2, energy and mass are COMPLETELY equivalent. So, an increase in energy IS an increase in mass!

ie. Object gets faster. Energy increases. Mass therefore also increases. Badabing, badaboom.

[kiwiberry]

Hey! When the device is connected to an electrical device, electricity is being removed from the system (ie. current is being drawn away to power that device). Thus, the person turning the generator has to add extra energy (kinetic to electrical) to make up for this net loss of energy in the system. So, the generator is harder to turn! Additionally, there may be eddy currents produced in the electrical device, which will also draw energy away.

Jake

Thanks Jake

More questions haha:
Would the answer to the first one be D? And I have no idea what the second question means, but the answer was 3<1<2

[jakesilove]

Thanks Jake

More questions haha:
Would the answer to the first one be D? And I have no idea what the second question means, but the answer was 3<1<2

I would say so! The more you speed up the motor (ie. accelerate), the greater the back EMF will cancel out the supplied current. So, I'd go with D

[jamonwindeyer]

Thanks Jake

More questions haha:
Would the answer to the first one be D? And I have no idea what the second question means, but the answer was 3<1<2

That second question isn't examinable - Where's it from

The actual reason it is 3>1>2 is because voltage is a change in electric field strength. Electric fields are stronger when their field lines are closer! So in 3, the potential difference is positive because the field is stronger at Point B. Then it is zero for 1 because the field is the same in both. Then it is negative for 2 because the field is stronger at point A.