HSC Physics Question Thread

[Dragomistress]

Hey!
May someone help me with these three questions?
Thanks!

[jamonwindeyer]

Hey!
May someone help me with these three questions?
Thanks!

I'll take the first one! It is A - Max Planck absolutely believed that science should play into politics, and he certainly practiced in Germany. That leaves A as the only possible answer

[justwannawish]

Hi!
Could someone explain this to me? The answer's A

[Fergus6748]

Hi!
Could someone explain this to me? The answer's A

Hi so basically because of Lenz's law, a south pole would form at the end of the solenoid to oppose the movement of the magnet, so that means on the other side of the solenoid would form a North pole. Thus that means the magnetic field at P will flow from left to right, and using right hand rule, pointing your thumb towards the north end you can find that the current is travelling anticlockwise so from X to Y. Hope this helps!!

[elvis810]

Could someone help me with this question? The answer is D. Please explain why it moves up. Thanks!

[justwannawish]

Hi so basically because of Lenz's law, a south pole would form at the end of the solenoid to oppose the movement of the magnet, so that means on the other side of the solenoid would form a North pole. Thus that means the magnetic field at P will flow from left to right, and using right hand rule, pointing your thumb towards the north end you can find that the current is travelling anticlockwise so from X to Y. Hope this helps!!

Hey,
Thank you so much for answering! I get the field bit and that the current travels anticlockwise, but I don't get why it can't go from Y to X?

[blasonduo]

Hey!
May someone help me with these three questions?
Thanks!

Hey! I'll do the 2nd one!!









This gives me the answer of C

Additional note: Now, what is really weird (but freaking awesome) is that you notice that the distance is not dependant in the equation, yet it is work, and work always coincides with how far it was moved (work is force times distance for crying out loud!). Even if I had the plates 100m apart, and this particle moved 50m, the amount of work done would be the same, and this is all because of the Force the particle experiences. An example would be throwing a ball, you throw one on earth with a certain amount of energy, it will go up a certain height. Go to the moon and use the same energy, the ball will go higher because there is less gravitational force, even thought you put in the same amount of work. The fact that this just kinda cancels out is super gobsmacking in my opinion, I love physics

[jamonwindeyer]

Could someone help me with this question? The answer is D. Please explain why it moves up. Thanks!

Welcome to the forums Elvis!

I'm thinking the answers mean the ring is what jumps, but the logic is the same regardless. When we flick the switch, we have a current flowing into the coil. This introduces a magnetic field - Now it is constant once the current is flowing, but while it ramps up, it is changing. That changing field induces eddy currents in the ring.

Now the induced current will act to oppose the change which created it (Lenz's Law). The ring wasn't in a magnetic field, now it is, so the eddy currents will act to create forces to get the ring away from the field. Rotating won't do this, not moving won't do this - Jumping up will do this! Hence the answer!

This is the intuitive explanation without an exact analysis of forces, but this does the trick for this question!

[owidjaja]

Hey guys,
So tomorrow's my physics exam and I'm still unsure on the quanta to quarks stuff. Is it better to cram for that or just do more past papers? I love exam clashes

[jamonwindeyer]

Hey guys,
So tomorrow's my physics exam and I'm still unsure on the quanta to quarks stuff. Is it better to cram for that or just do more past papers? I love exam clashes

Normally practice is the way to go, but you gotta make sure you know your content, at least a little. So I'd say cram quanta for an hour or so, just download a set of notes and read, try and remember the main points. Then get some sleep!!

[elvis810]

Welcome to the forums Elvis!

I'm thinking the answers mean the ring is what jumps, but the logic is the same regardless. When we flick the switch, we have a current flowing into the coil. This introduces a magnetic field - Now it is constant once the current is flowing, but while it ramps up, it is changing. That changing field induces eddy currents in the ring.

Now the induced current will act to oppose the change which created it (Lenz's Law). The ring wasn't in a magnetic field, now it is, so the eddy currents will act to create forces to get the ring away from the field. Rotating won't do this, not moving won't do this - Jumping up will do this! Hence the answer!

This is the intuitive explanation without an exact analysis of forces, but this does the trick for this question!

Thank you!

[dermite]

Hi there, im struggling with understanding the operation of a galvanometer and loudspeaker (in simple terms) for the respective dot point of the motor effect.
I'd appreciate help on the subject.
thanks

[elvis810]

I'm not sure where to start.

An 80 kg daredevil stunt person jumps from a helium-filled balloon at an altitude of 20 km. When at an altitude of 10 km, the stunt person is falling at 250 ms-1 through the atmosphere. The amount of heat and sound energy produced by the friction while the stuntperson falls through this 10 km distance is closest to:
(A) 2500 kJ
(B) 4560 kJ
(C) 5350 kJ
(D) 7850 kJ

Thanks again for all your help!

Hi there, im struggling with understanding the operation of a galvanometer and loudspeaker (in simple terms) for the respective dot point of the motor effect.
I'd appreciate help on the subject.
thanks

A galvanometer consists of 2 curved magnets, a spiral spring and a pointer connected to a coil which is wrapped around an iron core. When the galvanometer is connected to an external circuit, current flows through the coil. The coil will experience a force as it is inside a magnetic field (motor effect) and starts to rotate. As the coil rotates, the spring is stretched and the opposing torque exerted by the spring increases. When the opposing torque of the spring is equivalent to the forward torque of the coil, the coil will stop rotating. A scale is calibrated such that the pointer reads the current through the coil.

A loudspeaker is a device that transforms electrical energy into sound energy. A coil of wire (known as the voice coil) sits in the space between the pole pieces of the magnet. Electrical signal inputs to the loudspeaker are in the form of alternating currents. When the current flows through the coil, the coil experiences a force as a consequence of the motor effect. This force will cause the coil to vibrate back or forth depending on the direction of the AC.  The voice coil is connected to a paper speaker cone that creates sound waves in the air as it vibrates.


Mod edit: Merged double posts --Calebark

[S200]

I'm not sure where to start.

An 80 kg daredevil stunt person jumps from a helium-filled balloon at an altitude of 20 km. When at an altitude of 10 km, the stunt person is falling at 250 ms-1 through the atmosphere. The amount of heat and sound energy produced by the friction while the stuntperson falls through this 10 km distance is closest to:
(A) 2500 kJ
(B) 4560 kJ
(C) 5350 kJ
(D) 7850 kJ

Thanks again for all your help!

Hey there!
SO, for this, use Gravitational Potential energy vs Kinetic, and the energy loss must be heat/sound.
So;

[Mate2425]

Hi guys, could someone please help me in getting a basic understanding with examples of rotational and transitional velocity - Astrophysics.

Thankyoou!