HSC Physics Question Thread

[Maraos]

Hi! 
I was just wondering what would be the correct extended response answer to the following dot point in the option topic Quanta to Quarks?
Dot point 2.4: Explain the stability of the electron orbits in the Bohr atom using de Broglie's hypothesis.

What would be the main issues i need to raise?



Thanks!

[kiwiberry]

Hi! 
I was just wondering what would be the correct extended response answer to the following dot point in the option topic Quanta to Quarks?
Dot point 2.4: Explain the stability of the electron orbits in the Bohr atom using de Broglie's hypothesis.

What would be the main issues i need to raise?

Thanks!

Hello!
So, de Broglie proposed that all moving particles have wave properties, with wavelength given by \(\lambda=\frac{h}{mv}\). He suggested that electrons must exist in orbits made of an integer number of wavelengths of the moving electrons (\(2\pi r = n\lambda \)) so that they would form standing waves - these don't propagate and are therefore stable and will not lose energy. If electron orbits contained a non-integer number of wavelengths, the electrons would destructively interfere with each other and lose energy. Hence de Broglie's hypothesis was able to provide a quantum explanation of the stability of electron orbits in Bohr's atomic model.

Hope this helped!

[Maraos]

Hello!
So, de Broglie proposed that all moving particles have wave properties, with wavelength given by \(\lambda=\frac{h}{mv}\). He suggested that electrons must exist in orbits made of an integer number of wavelengths of the moving electrons (\(2\pi r = n\lambda \)) so that they would form standing waves - these don't propagate and are therefore stable and will not lose energy. If electron orbits contained a non-integer number of wavelengths, the electrons would destructively interfere with each other and lose energy. Hence de Broglie's hypothesis was able to provide a quantum explanation of the stability of electron orbits in Bohr's atomic model.

Hope this helped!

Thanks so much for the info!

[Mymy409]

In projectile motion, if we find, say, the initial horizontal velocity in the first part of the question and round it up, do we use that value to find other values? Or do we use the unrounded value?

[Shadowxo]

In projectile motion, if we find, say, the initial horizontal velocity in the first part of the question and round it up, do we use that value to find other values? Or do we use the unrounded value?

Use the unrounded value when you can

[jamonwindeyer]

In projectile motion, if we find, say, the initial horizontal velocity in the first part of the question and round it up, do we use that value to find other values? Or do we use the unrounded value?

You'd be marked correctly for both (I'd wager), but if it is easy to use the unrounded value, use it. Otherwise, take a few extra decimal places. If they ask to find a rounded value in Part (a), you can use the rounded value in Parts (b), (c) etc (for example)

[Maraos]

This question is driving me insane. 
Apparently the answer is A but I don't see how.
Isn't A moving in a clockwise direction??, isn't the left side a south pole and the right side a north pole, according to the right hand rule?



Any help would be great!
Thanks 

[jamonwindeyer]

This question is driving me insane. 
Apparently the answer is A but I don't see how.
Isn't A moving in a clockwise direction??, isn't the left side a south pole and the right side a north pole, according to the right hand rule?

Any help would be great!
Thanks 

You are right about the polarity of the magnetic field, but watch the current, it goes in the opposite side - The right hand side of the coil has current going upwards (into the page?), use the right hand slap rule and you will get anti-clockwise!

Would you have picked another option? Will do my best to explain over text, aha

[Maraos]

You are right about the polarity of the magnetic field, but watch the current, it goes in the opposite side - The right hand side of the coil has current going upwards (into the page?), use the right hand slap rule and you will get anti-clockwise!

Would you have picked another option? Will do my best to explain over text, aha

Ohhhhhh....
I was using my right hand palm rule wrong...... I didn't point my fingers in the direction of the field, I was pointing towards the North pole........
I probably shouldn't be studying for trials this late at night hahaha
Thanks for the help!

[arunasva]

Hey can someone please tell me how to find the length in part b of this question so that i can do


t = fd = mgl  to get to my answer. Thanks

[kiwiberry]

Hey can someone please tell me how to find the length in part b of this question so that i can do


t = fd = mgl  to get to my answer. Thanks

I think it's 0.1m (the radius of the pulley) because the force is applied at the circumference, not 100% sure though!

[jamonwindeyer]

I think it's 0.1m (the radius of the pulley) because the force is applied at the circumference, not 100% sure though!

Vouching

[arunasva]

I think it's 0.1m (the radius of the pulley) because the force is applied at the circumference, not 100% sure though!

you're a ledge(end) im hangin on to you

[12carpim]

Hey,
I'm stuck on question B from the physics textbook. I continue to try and find where I am wrong because my answer is never the one they have in the book, if someone can have a crack at it and validate my answer.
Thanks 

[jamonwindeyer]

Hey,
I'm stuck on question B from the physics textbook. I continue to try and find where I am wrong because my answer is never the one they have in the book, if someone can have a crack at it and validate my answer.
Thanks 

Does this match your answers?