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Pearson Physics 12 states: "When the light sources have the same intensity but different frequencies, they produce the same maximum current" However, Phet Simulation Photoelectric Effect seems to show that photocurrent changes with light frequency (eg see below for different photocurrents at...

The attached probem tricked me because the answer is apparently D and not A. Presumably because the magnetic field is weaker with 2 bar magnets joined N/S compared to a single bar magnet. So this seems to be a gap in my knowledge as to the resulting strengths of magnets joined together. Are...

Ok then does it sound better to replace "parallel" with "which have a component that is parallel"?

Every force has to have a non-zero component parallel to the motion to contribute to work in that direction ie W=Fscostheta.

Your definition of "work is energy" and "energy is work" contradicts many published definitions of the meaning of "work" in physics. https://en.wikipedia.org/wiki/Work_(physics) "In physics, work is the energy transferred to or from an object via the application of force along a displacement."

This is my latest attempt at trying to summarise but I feel there maybe a mistake in the wording. Any help would be appreciated. Thanks.

I have never asked about a massless rope. A description of the simple situation of the real rope shown above would have been all that was necessary. Thank you.

If so, is it saying that the tension in the rope at one end is 240N but 236N at the other?

Is this an accurate diagram? https://digestiblenotes.com/physics/Newton/third_law.php

That makes sense. Thank you both.

The inviolable formula (as you put it) is actually a=Fnet/m. m=0 does not prove Fnet = 0. To say that any rope accelerates (but has the same force applied to each end) seems very wrong.

Sure, but how do you know how big to draw your system to capture all action/reaction forces?

So I don't undertand how it can be said that the tension is the same throughout the rope (post#6) if they are very different at either end? I also don't understand how the net force on the rope must be zero just because the mass of the rope is zero (post#6).

OK so is there a similar action/reaction pair (applied force/rope tension) at the stronger team end?

OK so the weaker team and rope tension at that point are an action/reaction pair?

Ok let's go back to basics: Typo from me in last question..is the force of the weaker team on the rope considered a reaction force to the force of the rope on the weaker team? ie are they an action/reaction pair?

Haruspex, The question is very clear, and repeated a number of times now, is the force of the weaker team on the rope considred a reaction force to the weaker team applying a force to the rope? If you cannot answer that question then that's fine, but please have the decency to let somebody who...

Again, the forces on the ends of the rope are not at all equal because the rope is accelerating. I am guessing that the size of the tension force is always equal to the size of the force supplied to the rope by the weaker team. Is this considered a reaction force by the rope to the applied force...

My question is about the forces on the accelerating rope and the tension in the rope, its not about the forces on the ground. So I am not understanding your statement: "If we take the rope as massless then there can be no net force on it, and the tension is the same along its length. It is...

But they are not equal forces applied by the teams. That is why the question says that the system is accelerating to the right.

OK so in the following situation, if the teams and rope were accelerating to the right, is the tension in the rope a reaction force (therefore equal in size but opposite in direction to any of the applied forces)?

How would you come to the conclusion that trolley must be accelerating if you were to just analyse the trolley with the hands and ground friction being the external forces?

Trolley should have zero acceleration.

eg. For a ball in free fall (ignoring air resistance) there is only one force acting if the system is just considered to be the ball. It seems necessary to go to the system which includes the Earth for identification of the reaction force to be made. Is there any rule for how big a system must...

OK so binding energy is not the energy that is released, but it is equal to the energy that is released?

Thanks. I am trying to apply my understanding of charges experiences forces from interacting with electric field lines, to what's happening in the Crooke's tube here. I said down beacuse that was the relative location of the anode to the cathode in the diagram, nothing to do with gravity.

OK so here is a photo of a real one. Are the field lines curved down toward the anode?

Thank you its starting to make more sense. I am still a little bit confused however. Binding energy is released when a nucleus separates into its components, and it was energy not mass when it was stored in the nucleus? It was energy capable of doing work against any force which tried to tear...

Ok so is it true to say that binding energy is the energy released during a nuclear reaction?

OK. So what are the electric field line patterns in the Maltese Cross Crookes Tube?

So it would have worked the same without an anode?

The attached diagram shows the cathode rays moving in straight lines forward but the anode is beneath them?

What makes mass a form of energy rather than energy a form of mass?

But when I look at the definition of binding energy that doesn't make seem to make sense. It looks as though they had more energy when they were together and when they were separated that energy turned to mass (the mass defect)? Am I looking at this right? I also don't understand this...

Thanks haruspex!

See working attached. My problem is that I have come up with 3 equations but 4 unknowns (mq, up, vp, vq). Is this problem solvable? The answers say: a) 0.5 m/s b) 0.65 m/s and c) 0.34 m/s Many thanks

Thanks Weirdoguy and Ibix I think that's exactly what I am after.

I mean "absolute constant", in the sense invariant.

Thanks I understand your points. I wasnt very clear.My question is what is the evidence that supports that c in a vacuum is a constant. I am not really talking about the experimental evidence for Special Theory of Relativity and the evidence for time dilation, mass dilation (electrons having...

I understand that it is one of Einstein's postulates, however I don't know of any direct experiments which show that it is true.

Amazing ! thanks vanhees71 If light was imagined to leave with energies of discrete amounts, how did he end up with a continuous blackbody curve as a predicted result (rather than a series of points)?

yes I read that, so I am wondering why you wouldn't use a camera (viewed on a monitor) to just select from the outer light ring?

Yes thank you so much phys guy..that makes perfect sense. I am still not quite sure why they have to wait for an eclipse, I would have thought they could just sample light coming from the outer edge of the Sun, but anyways I am sure they have their reasons ;)

Thanks Delta2 that makes sense.

Interesting thank you vanhees71. Im not sure how Planck could have stopped at modelling the energy being released from matter in discrete packets, and in particular reconciled that with a view that the light energy was being released as a wave? How else could he have imagined the light energy...

According to this link you just have to anlayse the light that isn't coming from a place on the star that has a light the source directly behind it e.g wouldn't looking at light from the outer edge of star give you an emission spectrum? http://www.thestargarden.co.uk/Spectral-lines.html

Thank tech99 I am thinking the same thing. I will change the gas entry to the centre of the tube and place a hard plate at the end. The speaker end is perfectly sealed witha balloon so there shouldn't be much problem there. I just tried with propane and its a lot better. Although the flames now...

However I need to know whether Planck also had to assume that emitted light was quantised to make his model work? I need to teach this topic in the context of how different experiments shaped our understanding of the light model. I have found 2 sources which seem to contradict each other:(...

There are 70 jets of 1/16" diameter along the tube and I neeed to create flames 1" high. I know the calorific value of natural gas is much less than LPG (39 MJ/m3 Vs 93 MJ/m3) . I am not sure what assumptions to make from there in order to compare the predicted natural gas to the LPG volume...

Thank you so much Baluncore that all makes sense! Unfortunately I have already bought the Aluminium tube 100mm diameter so I will have to make the best of it. I think I might go polished top near holes and then black matt painted body.