New student here, sorry if this is a dumb question. My physics teacher gave us a problem of a cannon on a cart firing a cannonball assuming no friction.

The cart and cannonball together weigh 100kg and are moving at 3m/s. The cannon fires the cannonball, which weighs 10kg, horizontally at 29m/s. How fast would the cart be going afterwards?

He says that because momentum is conserved the 290 kgm/s that the cannonball has leaves the cart and the cart is going 0.1repeating m/s.

Intuitively, it seems because the cannonball is being fired there is extra force and there should be more the equation, but I could just be confusing myself. Is this the correct way to do it?

Why wouldn't this work?

If I just add milk and sugar to a cup and swirl it for a few minutes, dissolving the sugar, would I not (at least partially) create the conditions for the chemical reaction yielding disaccharide sucrose?

Wouldn't this mimic the chemical reaction in ice cream, making a sweeter, and creamier cup of coffee?

I tried it this morning and it SEEMED like it made a difference in the taste. But that could be my imagination.

Would this work? If not, why not?

Say, in the Schrödingers cat thought experiment, we replace the cat with something like a speaker, which will play one of two different songs based on the result of a random quantum event.

What would the experimenter hear (song 1 or song 2… or both😭)? This is probably a really stupid question but I’m still curious about it

I am a may 2025 IB exam student currently trying to find a topic for extended essay which I got from physics and I am thinking about doing it about the fishind rods? something like how does the thickness of the string and lenght of the rod affect the tension in the string, or any other opinions, advice you could give me

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Two bodies of mass m1 = 30 kg and m2 = 20 kg lie on a smooth horizontal surface, a horizontal force of 100 N acts on the body of mass m1, what is the acceleration of the body, the force that divides the mass m1 on the mass m2 and inversely

Assuming a hypothetical universe, where time is multidimensional (n-dimension) entity much like space has 3 dimensions and unlike how we have mostly studied it as 1 dimension to give a measure of seperation between events, in our most undergraduate text. If someone here in this space can guide me, I am curious to learn :

• a) What existing mathematical/physics works are done that I can read up on? (Would appreciate a direction for search)
• b) What mathematical concepts should one be familiar with to rewrite standard model equations with this assumption ?
• c) Does the answer to above a and b change when we introduce the concept of fractional dimension?

I was reading this writing (https://davidwoolsey.com/AttO/AttO_blog/Entries/2020/7/13_Black_Holes_and_Transverse_Tidal_Effects%2C_a_revised_essay_on_some_thoughts.html) about considering tidal effects in black hole models.

Outside of the main topic of the writing, there is a part that got my attention:

The authos indicates that in the context of Hawking radiation, only particles (like photons) with small enough orbital angular momentum will escape to infinity.

This made me think: could there be black holes with extremely large angular momentum that could transfer themselves part of it to escaping photons (even if they initially had small amounts of angular momentum upon escaping)? For example, I was thinking, if a black hole with an enormous spin emitted Hawking radiation and while escaping it made contact with the photon ring or the ergosphere (regions with high angular momentum), perhaps the photons could acquire quite a bit amount of angular momentum from these zones (which would be given by the black hole itself) trapping the photons forever, or even making them return to the black hole. Could this be possible? Is it possible that black holes trap their own Hawking radiation?

I mean for example light is an example for electric field being a component of a transverse wave.

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I am currently reading on exciton polaritons and reviewing transverse and longitudinal waves having ε(w)w²/c² = k² (k.E = 0) and ε(w)w²/c² = 0 (k//E) relations respectively and not sure about if k//E specified consciously or just to not use a different vector field notation but I needed to ask if E can be component of a longitudinal wave.

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I know both wave types always have the wave vector component (or property idk) so is it physically possible to have a wave vector and an E field parallel?

To clarify, if a planet has enough spin on it, could the centrifugal force cancel or greatly reduce the planet’s gravity?

So basically the person on that planet would be in a geostationary orbit a few centimeters above the surface I guess.

Assume a perfectly solid 1-piece spherical rock, like a planet-sized billiard ball.

Hi guys, STEM student here.My professors teach shit. I don't get a thing I understand. Ever since I started studying Physics as a separate subject instead of just Science, the condition has become worse. The professors just come, give lectures and leave, like the traditional ones. No practical, no computer simulation, no efforts. They made me feel like Physics is horrible. Ever since I've joined some subreddits for Physics, I've been interested in them. But yet, I'm not able to understand the questions on the exam papers. How do I academically get better at physics and learn it from my heart? Like , you know for maths, you just know it naturally without studying. You just need the logics and thinking power. How do I apply the same for Physics? I have my final exam in 25 days roughly and I really NEED to ace this subject. It just doesn't match that I am interested in physics but don't end up scoring as much as I expected. Can you help me through this?

What should the specs of my laptop look like if I only want to use it for my undergrad in Physics??

I've struggling with this question regarding biomechanics. Linked is the question and below is my current train of thought.

https://imgur.com/a/xJ9cnvB

I understand Torque is equal to force x distance. I assume the fulcrum is point "A" but I'm having difficulty finding how to do the trigometry side to be able to determine the torque. I've only ever dealt with questions without any angles involved so I really need some guidance to see how I should approach this question.

Many thanks

I am studying Maxwell's equations and I was wondering if it's possible to use a constant change in the flux of the magnetic field to generate a constant (static?) electric field (and if not, why not). Then the circulation (circuitation? idk the english term) should be 0 like when the electric field is static? If not, is the induced electric field intrinsically not conservative? Why?

Like, the longer is the application of force, the bigger should be the work, shouldn't it? Because if I move a rock with a force of x and the other one moves it with a force of 100x, but the distance is the same, we will kind of reach the same result; however, if we did it for a fixed amount of time instead of distance, then the other one would have a 100 times better result, and the value called "work" should kind of symbolize how resultative some action was, shouldn't it?

Quantum tunnelling can make a particle reappear in another place faster than it would be able to, if it travelled at the speed of light. So in some hypothetical future, would tunnelling be able to make all particles move into an infinitely dense configuration, thus creating a new big bang?

I've been hung up on this because of the universe's expansion. The particles in heat death still get further and further away at increasing speed, so it keeps becoming exponentially less likely that they tunnel into a singularity. Not only that, after a certain point every particle would pass the point where every other particle is moving away from it faster than light, making this even less possible.

Saying all that, is there something I've missed? Is it still possible, if unimaginably unlikely, given cosmic expansion?

I'll start with saying my highest level of education is highschool, I am currently undertaking tertiary education and want some clarification from elsewhere

Using the formula P = phg for water, with an specific gravity of 1.0, this is all with a tank open to atmosphere

https://imgur.com/a/staY0Ql

We say the pressure for 20 metres of water is P = 1.0 x 20 x 9.80665 and get a result of 196.133kPa which I am happy with, because the total height of the water is 20m above the sensor. I understand that the Pressure is linear with relation to the height. However the issue is when we have a primed line to a sensor and the sensor is placed about the water line, we have been told the pressure goes negative however I don't agree it can be a linear relationship below atmospheric pressure. If the sensor is 20m above the water line as shown, I have been told it is now P = 1.0 x (-20) x 9.80665, but how can we have -196.133kPa with a start atmosphere pressure of 101kPa, this would be below an absolute vacuum and doesn't seem possible and I am lost from there as I am struggling to find an answer online.

Please help me understand

Two objects, A and B, are both released from rest at the same time from the top of identical ramps. Both objects are hollow cylinders with the same radii, but different masses. Assume that the cylinders roll without slipping down the ramp. The mass, the radius, and the moment of inertia of both cylinders are found in the table below. Which object will be the first to reach the bottom of the ramp?

The answer is as below

When an object rolls down a ramp, its linear acceleration is dependent on its acceleration of gravity, the angle of the ramp, and the moment of inertia.

So they will reach the bottom at the same time.

But I still can't get it. I tried to use the formula a=αr then replaced α for τ/I (Newton's second law), and there is m in it (τ=mgrsinθ). Where did I get it wrong?

So I've understood for a while that in General Relativity it is at once true that a) there is no such thing as absolute velocity, all velocity is relative to your frame of reference, and b) nothing can travel faster than the speed of light, and as an object approaches the speed of light more and more energy will be required to accelerate it until it reaches a point where an infinite amount of energy is required to continue to accelerate it. What's long confounded me is how these two axioms can go together.

Let's say I'm traveling through space on a hypothetical space ship. This space ship has a supply of fuel that's effectively unlimited, and is continuing to accelerate under the power of a conventional thruster that, while powerful, has a finite maximum output. Now according to axiom B, at a certain velocity, in order to continue to accelerate, an amount of thrust will be required that is beyond my thrusters capability. This I understand; so far so good.

However, once we add in axiom A things get confusing, because my hypothetical ship doesn't exist in a Newtonian universe with a universal frame of reference, it's velocity can only be determined relative to other subjective frames of reference. Perhaps to a stationary observer my space ship is traveling below the speed of light, but what about an observer traveling in the opposite direction at similarly relativistic speeds? What if we are both traveling at above half the speed of light in opposite directions, would my space ship not be traveling at beyond the speed of light relative to that observer in motion?

It would seem that in order to determine how much more energy we need to continue accelerating at relativistic speeds we first require some frame of reference to determine that speed. Axiom A seems to suggest that which frame of reference we select is necessarily arbitrary, but Axiom B seems to contradict this, as what frame of reference we select determines what speed we are traveling, and therefor how much energy is required to continue accelerating or, even stranger, if we have already violated the speed limit of the universe.

So what gives? How can it at once be true that the universe has a speed limit and that all velocities are relative to a subjective observer?

Gravity is a force that attracts mass to each other. I understand that this force transforms potential gravitational energy (based on the distance and mass of the objects) into kinetic energy.

What I don't quite understand is what is the source of this energy? Where does the gravitational potential energy come from? It seems to me that mass basically produces an unlimited supply of gravitational potential energy, which would violate the law of conservation of energy.

Take, for example, the orbit of the Earth around the Sun. Earth's momentum pushes it away from the Sun, but the gravitational pull is strong enough to keep it in orbit. This means that the Sun is constantly exerting a force over Earth based on its potential gravitational energy. But where does this energy come from? Does mass produce an unlimited amount of gravitons? Does gravity turn space into energy? I get that their gravitational fields drive the force, but where is the energy lost in the process?

What is the significance of potential energy or in other words what do we mean when we say that something has potential is physics

so we had this q about what should be the minimum hight of a mirror for a man to see himself completly and it comes out to be half the height of man but shouldnt mirror smaller than that also show his full body if he goes far enough for eg i can see the stars, moon, sun etc in a mirror much smaller than their radius ?

If the de Broglie wavelength of a particle is given by lambda = h/p, how is the frequency determined?

What does it really mean by this? Especially the part on exhibiting wave like characteristics? Is it just a model to explain the behavior of light particles? Are the particles really moving in space time? or are the individual trajectory fixed?

So I have a question based on heat. Burning godzilla in 1995 Godzilla vs destroyah was at meltdown at 1500 C. With that type of heat and the fact it was still climbing ehat temperature would you need to cool it down drastically? In the film they use ULT lasers which is about 0 kelvin. Would that be adequate?

Weird question but it's for fun.

https://imgur.com/a/xYeO6ew

I calculated the energy required by subtracting the energy of products and energy of reactants and reported it. Why is this not the minimum kinetic energy required by the alpha particle?
If it needs more energy (Because the answer is greater than 1.86MeV) where does the rest of the energy go?

Thank you

Worded differently - if I love studying thermodynamics, what other topics am I likely to enjoy studying?

I think I have a pretty warped sense of how dense stars actually are. We tend to talk about space in very airy terms. Like 'gas giant' makes the planet sound big but intangible. Or stars forming from 'dust clouds' as if nebulae are like wisps of smoke. Plasma also feels very abstract, in that if you asked someone what plasma would be like physically, they'd probably imagine hot gas, or goo.

Then I think for a bit and remember that the gravity of the sun is massive, and it accounts for 99% of the mass in the solar system while being barely 100 earths in diameter. I guess it's hard to connect the concepts of 'extremely dense' and 'made up of gasses.'

If the sun was spread out such that the density is equal to that of our atmosphere, how large would it be?

So, Voyager 1 is 45 billion miles away, and it takes us 22.5 hours to send or receive a message one way. But we have also been in constant contact with Voyager since it was launched. So how did the delay express its self when there was no interruption of contact? I know that the delay is there, but was there some wort of slowing of communication as it got further away?

As I understand, acceleration in both RF and Plasma laser wakefield accelerators are very much constant. With the latter being around 80 GeV/m. Now, the only reason why LINIACs are efficient and radial accelerators cannot achieve the plank scale is due to the brehmstrahllung radiation of the magnets used for steering. Can neutron stars and other celestial bodies be used for steering the particles instead? My professor said the issue would be that neutron stars have extremely large magnetic fields. Where do those fields come from? Can we counteract it?

Is anyone familiar with known or suspected contradictions between set theory and Quantum mechanics? I ask because as I've had more interest in set theory it seems it's ontology is based on useful logical constructions that gets rid of Russell's Paradox but isn't an inherently proven aspect of reality. Which if that's the case to me seems is a surprisingly shaky ground for something like particle physics.

But also I just suspect I'm getting something wrong. If anyone has any related input that would be wonderful.