Gravity Definition and 1000 Threads

1. Problem Statement An astronaut is playing with a ping pong paddle and ball in zero gravity. The astronaut is 12m from a flat wall and floating toward it at 4m/s . A ping pong ball bounces back and forth between his paddle and the wall at 11m/s. Eventually, the astronaut reaches the wall and...

Homework Statement The reason why the heavy stone and light stone fall equally because of the ration of force to mass is same. can you explain it please what is ratio of force to mass is same?. Homework Equations F=ma and F=Gm1m2/r² The Attempt at a Solution As their acceleration is same...

I am no smart person like the rest of you, but I find it fascinating about how physics works. I am deeply motivated to know about how we would solve this problem about gravity and space flight. Would a particle accelerator be used to help solve this problem or am I way off base?

Yesterday I post a thread, this post is continue of that one. In pic 1 lift is accelerating. A observe inside the lift would assume that he is on planet. if he is on planet time slow on ground and fast in sky. Pic2 shows gravitational field, that have high magnitude in bottom, low at...

If the Earth gains 250 tons of weight everyday, over the course of hundreds of years wouldn't this alter the weight of a gram?

Hi everyone! I'm here for a little conveyance towards a question that is disturbing me for days. Just suppose, you and I design a hydroelectric generator that provokes energy from the downflow of precipitating rain. These falling drops of rain surely have originated from the vapours of the...

Hello All, I recently purchased a book on relativity called "Gravity in a Nutshell" by Zee. While it is interesting I find his conversational style to be too chatty. I prefer a little more of a "get to the point" conversational style. I'm going to be modeling the evolution of the...

Homework Statement 1. Do research to find out what artificial gravity is and how it is related to centripetal motion. Explain how artificial gravity could be created in a weightless environment and give a reason why we would want to do this.Homework Equations None. The Attempt at a Solution...

I'm embarrassed to admit that I am bit confused with concept of gravity. Here is practical example: When I stand on surface of the Earth majority, actually all mass is bellow me and gravity pulls me down. Let's imagine now that I am standing on the Earths iron core, majority of mass is above me...

To my way of thinking gravity must have been there at a very early stage for black holes to form, The thing is I can not find a definitive answer to my question. If gravity is a distortion of space time then matter must have come first, or were the distortions of space time a relic from the big...

For many years, the measurements of the Landé g-factor of the muon have been puzzling, as the experimental value and the theoretical predictions showed some disagreement - 3.6 standard deviations for the last years. Experimental and theoretical uncertainties have a similar size, so work on both...

It occurs to me that it might be possible to determine a local value of G by observing the tides over a long-ish period. Tide height might be distributed as a normal curve, but it might have a measurable deviance. I wouldn't expect a left/right offset of the X coordinate based on G(local) , but...

So, I have heard that the deflection of starlight using Newtonian gravity is only half of the deflection predicted by Einstein. NE1 know where I can find an example of the former calculation? thanks

Watching Star Talk. Had some interesting questions/ideas - such as what makes you a scientist - they think its 100% curiosity but our education system damps that all important curiosity. 100% agree - but IMHO the more important thing is as Feynman says - the ability to doubt and constantly...

I have been reviewing GR lately because as a mentor I find myself now answering more of those questions. I learned GR years ago from Wald and other sources, but since then have been exposed to the symmetries of the Standard Model. What struck me during this review is I now have a different...

Homework Statement A Gak it a type of alien that lives on a planet in another galaxy. One day a Gak decides to find out a little more about his planet. He drops a ball (it starts at rest) with a mass of 4.88 kg and notes that it takes 0.712 s to fall a distance of 4.04 m. What is the...

So recently I asked a question about a model of gravity I saw. Turns out I was misinterpretating it, it was the wronv source to use. Here is a video by PBS ( ) talking about what I was trying to say, that is that some people say 'The Earth rises to catch an apple, not vice versa. But, it...

Recently I watched a video on Gravity according to General Relativity. The video shows that the Earth rises up to catch the apple, what does this mean? It also shows the time axis being curved as the apple falls. Doesn't this mean that with enough time falling, the time axis will curve into a...

Hi, I found this rather interesting article on gravity and the zero point energy. Here is the link and abstract Abstract When Planck introduced the 1/2 hv term to his 1911 black body equation he showed that there is a residual energy remaining at zero degree K after all thermal energy ceased...

Has anyone else heard of that gravity waves may be the result of another type of supernova remains, called a Grav-Star? It seems almost to physically mimic a neuron star but stopped just shy of becoming a black hole, yet it still has enough of a gravity well to prevent light from escaping. Is...

I have an odd question after making a rubber band car. I'm wondering if placement of my pairs of wheels has any affect on how fast or how far my car goes. It seems to be a very impractical design, but I do want to know the science behind it. My question is if I move two wheels all the way to...

Hello. First post here so hi all. My question(s) is regarding the formation of solar masses by accretion of gases and dust. From what I understand, stars are formed by large clouds of gasses and dust particles pulling together and with enough gravity, (magnetic fields), and time. A fusion...

While waiting in the doctor’s office, I looked at a balloon sticker on the wall. That made me think (once again). Would it be possible to make something float without using your basic flotation stuff (helium and propellers mostly)? I was thinking in more of a futuristic themed way. Like magnets...

I was wondering if gravity was just the net interaction of the electrons orbiting the atom and the magnetic fields collapsing and recombining among each other somehow that made sense in my head.

In the Divine Comedy Dante describes travellers journeying through the Earth. He and his fellow travellers go down to the centre and continue and immediately realize that they are going "up". This indicates that gravity was understood to be a force or attraction coming from the centre on the...

So, from my last thread “Why doesn’t the water fall out of the Earth?” I asked if the reason why water doesn’t fall out of the Earth even on its tilted axis. Then the conclusion was gravity. To be more precise, gravity is the one that pulled the water on Earth into a ball form. What in gravity...

Most research into quantum-gravity is looking for a specific particle, the graviton, to represent the gravitational force at a quantum level. But they also acknowledge that it might be impossible to find the graviton particle, because gravity is so weak. Now, is it possible that we're looking at...

I'm not at all involved in QG but from far away I noticed : Spin 2 representations are 5x5 matrices. But in gravity what mathematical objects are quantized ? If it's the metric then it's a 4x4 matrix so that cannot be that. Or : how does quantization reveal a 5x5 matrix ?

Homework Statement I am having trouble linking gravity to the radius of the Earth and angular velocity. I was using this as a solid method to confirm the equation for values of a different sort based on centripetal acceleration. When inputting the values though it does not add up and I cannot...

Energy is required to make a body fall towards its surface i.e. to produce acceleration. That means energy will be lost by the body causing it. Energy is equivalent of mass. Therefore a loss in energy would mean a loss in mass. Right? I most sincerely apologise of I am wasting your time by...

[Moderator's note: This is a portion of a post originally made in another thread, which has been moved due to being off topic there.] Einstein's Equivalence principle is based on the realization that, "An observer in a windowless room cannot distinguish between being on the surface of the...

I'm curious about John Baez's book "Gauge Fields, Knots And Gravity" - I've read some of notes from his website and find his style of writing well matched to my style of learning. So, for personal interest, I was considering whether this book might be nice to read. That said, I'm not familiar...

I know this is probably going to sound stupid but I'm really curious for the opinion of someone who has knowledge. Well spacetime is like a stretched bed linen. Putting on an object with a big mass, will cause its curvature. Now imagine having a piece of fabric holding it stretced from both...

At high school, we saw without demonstration the fundamental principle of dynamics (2th Newton's law), i.e : $$\sum \vec{F}=m \vec{a}\,\,\,\,\,\,\,\,\,eq(1)$$ after, at university, we saw another expression of this 2th Newton's law : $$\sum \vec{F}= \dfrac{d\vec{p}}{dt}\,\,\,\,\...

I suppose the answer is no, since there is no reason to believe that it does. Or is there any? Has this been tested experimentally? Or is there an obvious reason that it does or does not?

Hi everyone, Me and a friend discussed a problem relating to a rotating reference frame, and somehow got to this question which we can't fully figure out, or maybe we are missing something. so, here goes: On Earth's equator, our tangential velocity is ~1700 km/hr. A satellite orbiting right...

Homework Statement A student can throw a football a max range of 60 meters. How far could he throw it if the Earth's gravity were reducted to 1/6 of its normal value , similar to the moon's gravity? Homework Equations v = .5at^2 The Attempt at a Solution I feel like i did this wrong but x =...

Homework Statement Two Jupiter sized planets are released from rest 1.0 X 10^11 m apart. What are their speeds as they crash together? I think my problem lies in figuring out which radius to use. In an equation like this are the radii of the planets included in the distance between them...

Homework Statement Homework EquationsThe Attempt at a Solution I first said it's B, since force throws up = positive. gravity down= also positive, please help asap thanks

Can we experimentally measure the very weak gravitational force between two objects just like we can detect magnetic field lines by a deflecting compass.

Hi there, so I want to know how to get the speed I need to move some object from point A to B, accordint to the distance between points, gravity and height angle. I means, I have this: height angle = 40.0 distance from point A to B = 5m gravity = -9.81 speed = ? I think that I just need to know...

Hi... The centre of gravity is the point where the whole weight seems to act on. How can this be possible? Ty in advance

Homework Statement An elevator is traveling at 30 m/s just as it touches a cushioning spring. The safety clamps engage at that moment and provide 20,000N of frictional force. The mass of the elevator is 3000kg and the spring constant is 15000 N/m. How fast will the elevator be traveling after...

Hi, what would happen if you took 1 cubic meter of matter from pulsar into empty space what would happen does the matter will expand since there is no more strong gravity does will it explode ? would like to know your answers

I have a major in mathematical physics and mathematics and currently I'm on a graduate course in Physics working on a master's thesis. When I started the graduate course I was going to work on General Relativity and Quantum Field Theory on Curved Spacetimes (QFTCS). It turns out that by several...

Homework Statement A jet pilot takes his aircraft in a vertical loop. V is 840 km/hr (233.3 m/s) find the min. radius of the loop to that the centripetal acceleration at the bottom does not exceed 6 Gs. Homework Equations a = v^2 / r F = ma The Attempt at a Solution I don't know where to...

I was reading this article Why Einstein did not believe that general relativity geometrizes gravity and it seemed rather interesting. So it would be interesting to hear what others think of it. It suggests that Einstein's view on GR was that it does not reduce gravity to inertia and geometry...

I'd like this issue clarified I understand that a full nonpertubative quantization of a yang mills gauge theory in 4D is unavailable. is Dirac quantization of classical theory of gravity e.g GR rewritten Ashtekar Variables Variables or some variation of the idea, a viable approach to a...

This is something I haven't been able to wrap my head around yet. In physics, I've always been told that gravity is a force that ALWAYS works between "objects" with mass. Now, it seems clear to me that if a feather and a hammer were to be dropped at the same time on Earth (without air...

How much gravity is needed to dim a light bulb? Could this exsperiment ever actuly be created? Also is the shape of a spiral galaxy like ours due to the effect of the supper massive black hole at its center has on all the other stuff in the galaxy ? Or is it because of the effect the black hole...