Okay, so this may seem a very &quot;simple&quot; question. I quote few lines from :  &quot;We can’t feel Earth’s rotation or spin because we’re all moving with it, at the same constant speed.&quot; &quot;Why don’t we feel Earth rotating, or spinning, on its axis? It’s because Earth spins steadily – and moves at a constant rate in orbit around the sun – carrying you as a passenger right along with it.&quot;  Okay, I get the fact that the ground, the atmosphere and all the &quot;things&quot; on Earth are moving at the same rate. It is almost like we are travelling in a train or an airplane, where we can walk normally as if on the ground, without feeling anything unusual. But, my &quot;Physics&quot; intuition seems to contradict this explanation. This is how I view this problem : We dwell on the ground and move with the Earth, very much like in a &quot;$2$-D Circular Motion&quot;, with the radius of the Earth as the radius of the &quot;circle&quot;. But the velocity changes every instant as its direction (which is tangent to the circle at the given point) changes constantly. The velocity is changing --- So there must be some acceleration , as Uniform Circular Motion is always an accelerated motion. So, I see that there is &quot;some acceleration&quot;. According to Newton's Equation $F_{\text{net}}=m.a$, we must be experiencing some Force, which is required to provide the necessary Centripetal Acceleration$(=\dfrac{v^2}{r})$. So, in short, I state my Problem as:  When we ride a Merry-Go-Round, we feel a &quot;certain&quot; force pushing on us, acting radially away from the centre. Why don't we feel the same &quot;certain&quot; force in case of Rotation of Earth?  EDIT : Can anyone please remove that &quot;Duplicate&quot; mark ? My question is not specifically about &quot;Why don't we feel the Earth's rotation ?&quot;. It is rather about &quot;Why (apparently) is Earth's Rotation not congruent/similar to some normal Uniform Circular Motion (as in a Merry-Go-Round) ?&quot;. Surely, I will re-word the question to be more specific.
121442
The Earth turns with a very high velocity, around its own axis and around the Sun.  So why can't we feel that it's turning, but we can still feel earthquake.
75380
I have problem understanding total angular momentum of earth about center of sun. Consider that earth has an orbital angular velocity of $\omega_0 \hat z$ and a spin angular velocity of $\omega_s \hat s$, distance between the centers of sun and earth as $R$ and radius of earth as $r$ and that earth has mass $m$. My understanding is that total angular momentum of center of mass of earth + angular momentum about CM of earth is $$L = m R^2 \omega_0 \hat z  + \frac{2}{5} m r^2 \omega_s \hat s $$ however a it's given in my text book as  $$L = m R^2 \omega_0 \hat z  + \frac{2}{5} m r^2(\omega_s \hat s + \omega_0 \hat z) $$  Why does the the $\omega_0$ appear when calculating angular momentum about CM of earth?
19205
The following is written in my textbook as the reason for weightlessness felt in satellites:     The gravitational pull is counterbalanced by the centripetal force.   This introduces two problems:   For satellites orbiting around Earth, gravity is, in fact, the centripetal force. If the gravitational pull and centripetal force on a satellite are both in the same direction, then how do they cancel each other out?
116246
So this is the question that's been bothering me:  Say you have a simple rigid body in space that is at rest or traveling with only translational motion at a constant speed. Say that the body is something like a rod and it's not rotating. So, at some point, an external force is acted on the rod, just for an instant and it is not acted along some axis that goes through the center of mass. What will happen??  My guess is that it will start rotating about the center of mass (because of torque) + it will get some translational motion towards the direction of the force. Is that correct? and if so, how much of the force becomes rotation and how much translational movement and why??  Please forgive my English and thnx in advance!!
41173
I saw a video some days ago () of a schoolgirl successfully launching a balloon into space which later popped and landed ~47 km from launch site.  If I vertically launch an object (say via balloon or rotors) from the surface of a spinning planet with an atmosphere like ours, then as it rises, will the planet's surface move away below it, or will the object rotate with the earth? (Assume that there are no local strong winds relative to the atmosphere, and it is completely calm.) The latter would mean the atmosphere, being itself a collection of such objects (air molecules), also spins with the planet.  Related SE question:   It seems from common sense that since at launch the object shares the motion of the surface it would keep rotating with the planet, and hence would later land at the launch site. However, as it ascends, the lateral speed required to maintain the same angular velocity with the planet rises linearly. Where would it get this extra momentum/energy from? From the rotating atmosphere? How did the atmosphere get moving in the first place then?  It might seem a lot of questions for a single SE post, but they're all connected, so a single explanatory answer should suffice.
44284
Let's assume that there is nothing in the universe except Earth. If the Earth rotates on its axis as it does, then would we experience the effects of rotational motion like centrifugal force and Coriolis force?  The meaning of my question is: is Earth rotating relative to space?
71213
The common explanation/trope for the equivalence principle always has something to do with you being inside an elevator or spaceship, and your supposed inability to differentiate, say, gravity from a rocket, or free-fall from being motionless in empty space. For example, Wikipedia  "being at rest on the surface of the Earth is equivalent to being inside a spaceship (far from any sources of gravity) that is being accelerated by its engines." Many other sources say similar things, often making broad, sweeping generalizations like "there is no measurement you can make to distinguish the two scenarios."  Isn't that just plainly wrong? Gravitational fields aren't homogeneous. Here on the Earth, a clock on the floor runs more slowly than a clock on the table, and we have clocks precise enough to measure such small differences due to the gravitational gradient. But doesn't a clock in an accelerating spaceship run at the same rate no matter where in the ship you put it?  I searched the top 50 or so questions about the equivalence principle and found  that talks about tidal effects in gravitational fields, but the explanation is very confusing. As far as I can tell, it seems to be saying the "attraction" between the particles that arises as a result of slightly different gravity vectors is somehow equivalent to the actual mutual gravitational attraction the particles should have absent the external gravitation field. I don't see how that could possibly be the case.  Also in that answer is a link to  of tidal forces and the equivalence principle, which seems to be saying the opposite: that tidal forces are, in fact, a distinguishing characteristic between gravitational acceleration and rocket acceleration, and that the equivalence principle only exactly applies to small enough points in space over a small enough duration, where tidal effects are negligible.  I know what seems most correct to me, but as I'm not an expert in this field, would an actual expert please shed some light on these varying views of the equivalence principle?
115404
I am having trouble understanding how centripetal force works intuitively.  This is my claim.  When I have a mass strapped on a string and spin it around, I feel the mass pulling my hand. So, I want to say that the mass is trying to move away from the center of the circle, and yet centripetal force makes it move in a circle, i.e, centripetal acceleration towards the center.  Similarly, when I am driving a car and making a curve, I feel being pushed away from the center of the curvature rather than towards it.  I am having so much trouble with these types of problems because of this counter intuitive concept.  Can someone help me out?
24928
According to General Relativity I am being accelerated upwards by planet earth while writing this question. But a curious person on the the other side of the planet relative to me would have the same experience. That means we are accelerated in opposite directions, although earths diameter do not seem to increase. How can this be?
25503
A friend showed me a  (a special kind of spinning top) lately and asked me about the physics behind it. I thought about it for a while but cannot quite figure it out. So I will throw the question to SE. Below is a picture of tippe top:  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  So basically the strange effect is that when you spin such a top fast enough with its round surface touching the table, the top will wobble and eventually invert itself. There is a  and here is an illustrative picture:   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  So my questions are:   Why is the top so unstable? Why does it invert? Why does the initial angular velocity of the top matter? (Why do we have to spin faster than a certain velocity in order for the top to invert?) What other shapes will lead to inversion?   I am looking for some intuitive explanations that do not involve too much mathematics. Heuristic approaches are welcomed!
54254
As I was trying to work out the expression for the apparent "g"-in case of the rotation of Earth-I was considering the centripetal force (m$w^2$r) and the weight (mg) all the time, thinking these were the forces that were acting on the body.     But later I found out that it should have had used centrifugal force instead of centripetal force. But why? We should be considering the forces acting on the body right? And it's the centripetal force that is acting on the body (with direction towards the center of the small circle).
99658
I remember the first time I saw this formula, $F = ma$, and it seemed perfectly correct and natural to me (in the sense that it is very straight-forward and logical, not that it is easy by any means). But then, I wondered, what if an object is moving with a constant speed? Maybe a car. If it travels with constant speed and hits me, it still hurts. So it's force must not be $0$.  One more thing related to this problem. If the same car is pulling another car behind it, if the car goes with constant speed, it implies that the first car doesn't exert any force to the second car at that moment, since it is not technically pulling it anymore (espacially if we don't take into consideration the friction).  So my question would be the following: How do these two phenomenons describe the same law of motion?   PS: If gravity wasn't behaving as some kind of acceleration pulling me constantly to the Earth's core, then if I jumped upwards, would I start slowly getting away from Earth?
106357
Acceleration causes inertial force, and it is not relative, but why? What is the reason for feeling inertial force by acceleration?
123462
For a long time I have wondered if there is a way to show that the rotational analogs of Newton's Laws are a direct consequence of just those laws, or are we adding more to them?  I understand mathematically that we take Newton's second law and do "r cross both sides," but that has always struck me as using more than just the 2nd law.  Here it matters where forces on the body are applied, but I don't see where Newton's Laws talk about points where forces are applied to a body. For translational motion it doesn't matter.  So are we adding a sort of "extra law" when we do this for rotation?  The only thing I can think of would be to "disassemble" an extended body into differential point masses and work with internal constraint forces that make the body rigid. If every mass is just a point mass it would get around the issue I'm having.  I've never seen any discussion along those lines, though.
36941
Let's take a planet identical to Earth, but with rotation speed multiplied by ten thousand. What would happen with the gravity if it was spinning madly around itself? Would the centrifugal force make objects seem lighter than on normal Earth? Would the people on that planet be able to jump higher?
3173
Clearly, the Earth is accelerating (as it has centripetal acceleration), and thus it is a non-inertial frame of reference. Then, why don't we use pseudo forces all the time? My teachers told me that the effect produced by the centripetal acceleration of the Earth on our calculations is negligible and hence we can safely neglect pseudo force. But how? I want rigorous proof with examples that show exactly how much we are compensating in exchange for neglecting that the Earth is a non-inertial frame of reference.
14578
The origin of spin is some what a puzzle to me, everything spin from galaxies to planets to weather to electrons.  Where has all the angular momentum come from? Why is it so natural?  I was also thinking do photons spin? we always think of the wave as a standard 2d sin wave but could this rotate in 3d? What implications would this have?   And what about spacetime how does all the spinning effect?  This has always been avoided in all lectures and classes I ever went to.