Rest Definition and 558 Threads

I need insight on the highlighted part; Total height ##= 2h + h + H## In my understanding, the displacement on either side would be the same, that is ##=h##m given the condition (assumption) that ##a=0##.

In my approach, ##T - R = ma## ##4.5m - 4m = ma## and ##s = \dfrac{1}{2} at^2## ##a=0.5## therefore, ##30 = 0.5 ×0.5 ×t^2## ##t^2 = \sqrt {120} = 10.95## seconds ##≈11## seconds. Your insight is welcome or better approach...

De Broglie Wavelength is λ = h / p. So at rest, v=0, and p=mv, so p=0. This means that λ = h/p = h/0 so we run into a divide by 0 issue, or infinite wavelengths for objects at rest. Is this line of reasoning flawed? Or can we consider v=1 for rest masses? Time Dilation is related to v. The...

Math qyuestion for AI (Skype) include an expression that x is resting on y (both straight line segments). AI insisted that x coincides with y, while my intent was only placing x on y. Does 'rest' have such a narrow definition?

I find it fascinating that all nucleons are three quark configurations. It is proof that each quark needs two others to remain stable. The hypothesis that early in the big bang there was a uniform foam of quarks and coalescence of threes formed protons begs the question: what percentage of...

Impossible?!? By my estimation the equation that describes this motion is given by: $$Pt = \frac{1}{2}m{ \dot x}^2$$ or $$\dot{x} = \sqrt{\frac{2P}{m}} \sqrt{t}$$ but this implies: $$\ddot{x} = \sqrt{\frac{2P}{m}} \frac{1}{\sqrt{t}}$$ So, no matter how small we make the power, we appear...

Hi, A body with center of mass behaves as a point mass when a force is applied. So when ##F_{ext}=0## then does it also behave as a point mass with ##a_{com}=0##, at rest. If yes, How can we prove this? (And can somebody please answer my other question I posted a week ago...

Summary:: I'd like to check my understanding of standard problems where a billiard ball resting on a plane is hit horizontally at some height above its center So the situation is that a ball of mass ##m## and radius ##r## is at rest on a horizontal surface. There is friction between the ball...

I have drawn a fbd and the logic I think is that at rest the block moves down the wedge but when a force P is applied vertical force becomes zero and the horizontal force ##F_N\sin \beta## = P?

hello according to GR gravitational force is not a real force rather a space time curvature ok a body in motion follows a sort of invisible rails why doesn't a body at rest remain at rest, then ?

It's a pre-print from a bunch of researchers at the NIH. https://assets.researchsquare.com/files/rs-1139035/v1_covered.pdf?c=1640020576 No wonder Long Covid exists! ?:)

My answer is (A) since I think the motion of the spacecraft will alter the length of the spacecraft (length contraction) but not changing the orientation so the angle will stay the same But my teacher said my answer is wrong. What is my mistake? Thanks

Here is where I am at : 1- F(C2/P) > F(C1/P) must be true I believe this is false, considering the angle separating C1 from the 'ceiling' is bigger 2- F(C2) > 10 N may be true I believe this is true because F(C2) could be broken down into vector components which may go above 10 N 3- Vector sum...

The proton and neutron are composed of up and down quarks. What is made up of all the rest quarks?

The mass (rest mass) of an atom, for example, depends on the kinetic and potential energy of the particles and their individual masses. Kinetic and potential energy are relative. Why is the mass not relative, but the same for all reference frames?

I know how to solve this using work energy theorem but how can one solve it starting from the fact that net force is centripetal? My attempt was "this means we only need an "anticentripetal" force of same magnitude, but centripetal force does 0 work hence new force also 0 work to counter it"...

Currently, the only part of the textbook question that is completely throwing me off is "an angle of ##l=\sqrt{2}c##". If I am not mistaken, how am I suppose to interpret that as an angle and calculate for the answers of (a) and (b) accordingly? As for my attempted solution process of this...

Hello, Just checking that my understanding is correct: the nervous system is formed by the central nervous system (CNS), which comprises the brain and the spinal cord, and by the peripheral nervous system (PNS) which bring signals from and to the CNS from and to the rest of the body. Both CNS...

___ Blaming people for "unhelpful answers" when you have an unclear question does not put the blame in the right place. Either your two 1's are distinct or they are not. If they are not distinct, you shouldn't have two of them. If they are, you shouldn't use the same symbol for them.

Question diagram, attempt at solution below I need to cancel some of the terms in the moment equation but a not sure which ones to start with. I don’t know μ so can not calculate FA, so should probably substitute FA = RB2.

Motivation for why I'm asking this: I'm trying to better understand why an object that is initially at rest with respect to a massive body will fall simply by virtue of the curvature of spacetime. If it were moving through space with respect to the Earth initially, I could see the curved path...

Hi, I was reading about the Pilot Wave theory. I also found this vid: Is the Pilot Wave theory against most of the other interpretations of QM? And what are the main things one needs to accept? - In pilot wave theory, --- we have to accept a medium of unknown particles. ---...

When a ball is thrown upward it becomes at rest at maximum height, at this it is not in equilibrium although it is at rest. It is not at equilibrium because force of gravity is acting on it? Still I cannot find good explanation from exam point of view.I also cannot find the figure/diagram.

equation of motion : while

I honestly have no clue where to start, any help would be great.

Hi every one, In Compton effect I understand that the electron is considered free electron because the energy of the incident photon is very much larger than the binding energy of the atomic electron. But iam not sure why the electron is considered to be at rest (v=0). please help. Thanks.

Free body diagram one each object: Block 1: Normal force upwards, weight downwards, tension to the right, friction to the left Block 2: Normal force to the right, tension upwards, weight downwards, friction upwards Cart: Contact force with block 1 downwards, contact force with block 2 to the...

I've come across some conflicting definitions and hoped someone more in-the-know could clarify a few points. The rest energy is the total energy of the system in its rest frame; I read about the following (approximate!) semi-empirical mass formula earlier, and if we multiplied this through by...

ok I chose e for the zeros

Hi there I have been having a go at this question and I'm uncertain if my answer to part b) is valid? The problem is when I plug this into the calculator I get 6.379... revs however this doesn't make sense to me. 2*pi is roughly 6.28 radians so doing 4.061... rads / 6.28 rads = 0.647 revs...

I'm working on E fields and particles in E fields, and I was wondering if particles are ever truly accelerated from rest. I did some reading on how accelerators work and cathode tubes, but it seems that particles are always in some type of motion. Is this just a thing for introductory level...

Question 1 Consider a sample at a height ##ℎ## below the interface of air and the fluid. The pressure on the sample is given by ##𝑃_𝑎=𝑃_{𝑎𝑡𝑚}+𝜌𝑔ℎ##. My question is does 𝑃𝑎 include the pressure due to the particles that are to the side of the sample? Question 2 Now consider this setup. In this...

so I can find the centrifugal force but shouldn't the Coriolis force be 0 because the mass is at rest?

I'm conscious I posted a question about a similar topic recently, however I can't seem to resolve an apparent contradiction. As an example, consider a deuterium atom with 1 proton and 1 neutron. When separated at infinity, each has a certain mass and a certain rest energy differing only by a...

My physics textbook states that increasing the GPE of an object will increase its rest mass by E/c^2 , though I don't think this should be the case. I would argue that increasing the GPE of the object-Earth system will cause the rest energy of the system to increase by this amount, whilst that...

[Mentors’ note: this thread was split from the FAQ at https://www.physicsforums.com/threads/rest-frame-of-a-photon.511170/] I am not an expert! As I understand it, Einstein considered, what a guy standing in a photon will experience if he look at his watch. My understanding says, that the...

Suppose we have two observers A and B and they are at rest. Observer A observes two objects falling from height H (A has same distance between the two objects). Does observer B will measure different times for the duration of falling of the two objects ? (because the two object are not in the...

Suppose there is a 1 million solar mass black hole. A 1.022MeV photon near a nucleus produces an electron-positron pair a distance=A from the event horizon. The positron’s vector is directly “up” away from the singularity. It doesn’t have escape velocity. It reaches an apogee at distance=B from...

The four-velocity and four-acceleration of a particle may be written as ## (V^\mu) = \gamma(\textbf{v},c) ## and ## (A^\mu) = \gamma \left(\frac{d\gamma}{dt}\textbf{v}+\gamma\frac{d\textbf{v}}{dt},c\frac{d\gamma}{dt} \right)##. where ## \gamma ## is the Lorentz factor, ## \textbf{v} ## is...

In classical physics, every object is obviously at rest with itself, and it makes perfect sense for this to be true. But would this violate the uncertainty principle for a particle? If you are the particle and you know that you're at rest with respect to yourself, you know both your location...

this is the question and solution given in the book solution i made below. only difference is i took x as opposite side that given in the book and wrote F=ma equation that way. as a result the left side of equation (3) directly turned negative. that caused difference in result but why? i mean...

Consider a mass in its restframe relative to which another mass can have an arbitrary velocity ##v < c##. Now consider a photon in its hypothetical restframe. Can a mass have an arbitrary velocity ##v < c## relative to the photon?

Homework Statement In two rockets, one of which moves and the other is at rest, the motors are connected for a short time. During their operation they throw the same mass of gas (small in comparison with the mass of the rocket) at the same speed with respect to the rockets. The kinetic energy...

Homework Statement [/B] Two blocks A and B of masses m and M are connected to the two ends of a string passing over a pulley. B lies on plane inclined at angle theta with the horizontal and A is hanging freely as shown. The coefficient of static friction between B and the plane is us. Find the...

The answer is 3.079*10^-26 kg I tried doing E=mc^2 20*10^9*1.602*10^-19=m*(3*10^8)^2 m=3.56*10^-26 kg However when I do E=γmc^2 I get the correct answer. Is the question wrong, because isn't it 20 GeV of kinetic energy, not total energy?

Hello, I recently bought a Dyson vacuum and have been excitedly vacuuming my floors way more than I need to! I have been doing some thinking as well on the matter (yes, vacuuming) and have a physics problem/question. It has been a long time since I studied physics, so I am not equipped to...

Homework Statement Homework Equations Component of force,equilibrium of force. The Attempt at a Solution In the problem (ii),the friction force is ##Mgcosθμ##,the component of weight in the inclined surface is ##Mgsinθ## and the component of the applied force ##F## along the inclined surface...

A 30 kg sphere is held stationary by two cables. One cable is attached at 60° above horizontal. The second cable is horizontal and attached at the side of the sphere. Find the tension in both cables. Newton's 2nd law: F=ma, which means a = (∑F/m) We can also find the weight: W = mg Let's say...

[Moderator's note: Post spun off from another thread.] That is correct but it doesn't mean Eo=0. The rest energy is unlimited in classical mechanics. Therefore it is impossible to find a relation between total energy and momentum.

Homework Statement So i have this lab where I am supposed to push a car up an inclined ramp. I record the time it takes for the object to reachest the highest point on the inclined ramp before it goes back down. I am supposed to create a position vs time graph, velocity vs time graph, and...