# Tag Info

6

A centripetal force is not a fundamental force. We call any force a centripetal force if it is acting towards the center of the direction of rotation, perpendicular to the direction of motion. Rotating a rock tied on a string? Centripetal force = tension in the string Satellite orbiting Earth? Centripetal force = gravity Charged object rotating around an ...

3

If I understand you correctly, your two points about apparent slowness of speeds is related to scale, and disappears when you quantify it using a common unit. ie: We think of 10m/s as relatively slow because the average human is 1.8 metres in height, and we can imagine that 10 metres per second, or 36 kilometer/hour as an achievable speed using a machine ...

3

General relativity reduces to special relativity locally. What this means is that given an error tolerance $\varepsilon$, you can find an extended region (perhaps just a small one) around any point in spacetime such that the laws of physics as tested only within that region match those of special relativity to within $\varepsilon$. That means if you measure ...

3

It depends on how you "derive" Lagrange's equations, whether taking Newton's laws as fundamental or by assuming an action integral and minimizing it. However, there is no such requirement that you be in an inertial frame of reference. Thus, to look at your pendulum problem, you could start with the Lagrangian L = \frac{1}{2} I ...

3

I) In e.g. Ref. 1 is shown that there exist (possibly velocity-dependent) generalized potentials for all the fictitious forces, such as, e.g., the centrifugal force, the Coriolis force and the Euler force. So Yes, there exist Lagrangian formulations for non-inertial accelerated reference frames. II) OP's image shows Kapitza's pendulum. Kapitza's pendulum ...

2

Actually the COM for the 2-body problem is the essential feature in this subject and with respect to it, both the Earth and the Sun rotate. Indeed, motion is relative, the relativity of it is even easier to understand in the Galilean Relativity than in Special Relativity. The Heliocentric view is actually the correct opinion that the Sun of our planetary ...

2

The use of inertial frames in Lagrangian mechanics is by no means compulsory and everything can be done in any reference frame provided one takes all forces, real and inertial, into account. Actually there are two possibilities in interpreting the question. We work in a non inertial frame $R'$ (instead of an inertial one $R$) because we are adopting ...

2

Similar questions have cropped up on this site many times, and the debate surrounding them is usually fractious because people misunderstand each other's use of words like exist. One of the lessons of General Relativity is that any observer has to choose a locally convenient coordinate system that may not be globally convenient. We on Earth (quite sensibly) ...

1

why wouldn't that straight line be in the direction of acceleration why do you think the acceleration line be in the direction of tangent? the tangent is where a body would have kept moving if the rope didn't pull it. so the vector of speed changes towards... where the rope is attached, i.e. perpendicularly. acceleration is the change in velocity ...

1

It's a matter of what you mean by "see". Even for a distant observer, it will take a small amount of time for the gravitational redshift effect to become essentially infinite. If your collapsing gas star redshifts to the point where it won't emit a single photon in the age of the universe, it may not have yet technically "redshifted to zero", but it has ...

1

What is angular speed? Clearly it is $\frac {v_\perp} {r}$ where symbols have their usual meanings. Rod rotates about its, say, rightmost point, say $O$. We will consider left side as positive $x$-axis. Now consider a point $A$ at distance $r_1$ from it. Let the rod have instantaneous angular speed $\omega$. All points on the rod will have this $\omega$ ...

1

The actual question in this question, is a good physics question. Freely interpreted, it basically asks if SR effects, in particular time-ordering of spacelike separated events, make it difficult or impossible to simulate physics. The answer to that is no. An "external" Simulator (be it a particle physicist or the hypothetical people simulating our ...

1

The important thing is that all speeds seem to change: If you would look at the universe, in this case the two protons, from the perception of a man shrunk to the size of a proton, not only would the particles appear much faster, but so would the speed of light. So if you shrunk yourself to a trillionth of what you are now, one proton would have a diameter ...

1

This is the reduced mass. This effectively accounts for the fact that the center of the sun is not 'fixed', but rotates around the center of mass (also called the barycenter) of the Earth and the sun together. The expression $\frac{mM}{m+M}$ approximates to $m$ when $M>>m$.

1

You have to measure everything from the same frame of reference. Your own frame of reference obviously has a velocity of 0, relative to you. The other object moving toward you, or away from you, will never move faster than the speed of light as seen from your frame of reference. A third observer can see two objects, each moving at the speed of light. Toward ...

Only top voted, non community-wiki answers of a minimum length are eligible