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Questions tagged [acceleration]

The rate of change of velocity of a body per unit of time.

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271 votes
11 answers
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Don't heavier objects actually fall faster because they exert their own gravity?

The common understanding is that, setting air resistance aside, all objects dropped to Earth fall at the same rate. This is often demonstrated through the thought experiment of cutting a large object ...
ErikE's user avatar
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12 votes
3 answers
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Velocity in a turning reference frame

I often see the relation that $\vec v=\vec v_0+ \vec \omega \times \vec r$ in a turning reference frame, but where does it actually come from and how do I arrive at the acceleration being $$\vec a=\...
Xin Wang's user avatar
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29 votes
7 answers
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Why do two bodies of different masses fall at the same rate (in the absence of air resistance)?

I'm far from being a physics expert and figured this would be a good place to ask a beginner question that has been confusing me for some time. According to Galileo, two bodies of different masses, ...
merwaaan's user avatar
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7 answers
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Does a charged particle accelerating in a gravitational field radiate?

A charged particle undergoing an acceleration radiates photons. Let's consider a charge in a freely falling frame of reference. In such a frame, the local gravitational field is necessarily zero, ...
Sergio's user avatar
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107 votes
5 answers
109k views

How and why do accelerating charges radiate electromagnetic radiation?

Let's consider it case by case: Case 1: Charged particle is at rest. It has an electric field around it. No problem. That is its property. Case 2: Charged particle started moving (it's accelerating)....
claws's user avatar
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11 votes
6 answers
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Do photons have acceleration?

Photons travel at the fastest speed in our universe, the speed of light. Do photons have acceleration?
Eka's user avatar
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11 votes
3 answers
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How can you accelerate without moving?

I know this question has been asked in other forms, generally regarding the balance of forces. This time I want to focus on motion. I've got a laser accelerometer on my desk. It tells me that I'm ...
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63 votes
7 answers
12k views

Does a constantly accelerating charged particle emit EM radiation or not?

The Abraham-Lorentz force gives the recoil force, $\mathbf{F_{rad}}$, back on a charged particle $q$ when it emits electromagnetic radiation. It is given by: $$\mathbf{F_{rad}} = \frac{q^2}{6\pi \...
John Eastmond's user avatar
14 votes
10 answers
5k views

How do we know that $F = ma$, not $F = k \cdot ma$?

It seems intuitive that $a\; \propto \frac{F}{m}$, as the greater the force that is applied on an object, the greater its acceleration will be. Inversely, the greater the mass of the object, the ...
1110101001's user avatar
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61 votes
4 answers
20k views

If I'm floating in space and I turn on a flashlight, will I accelerate?

Photons have no mass but they can push things, as evidenced by laser propulsion. Can photons push the source which is emitting them? If yes, will a more intense flashlight accelerate me more? Does ...
Hello World's user avatar
65 votes
10 answers
40k views

Why does a free-falling body experience no force despite accelerating?

Note: For the purposes of my question, when I refer to free fall assume it takes place in a vacuum. From my (admittedly weak) understanding of the equivalence principle, falling in a gravitational ...
AdamJames's user avatar
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20 votes
5 answers
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How to get distance when acceleration is not constant?

I have a background in calculus but don't really know anything about physics. Forgive me if this is a really basic question. The equation for distance of an accelerating object with constant ...
ben's user avatar
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5 votes
1 answer
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Is acceleration due to gravity constant?

I was taught in school that acceleration due to gravity is constant. But recently, when I checked Physics textbook, I noted that $$F = \dfrac{G m_1 m_2}{r^2}. $$ So, as the body falls down, $r$ ...
user13107's user avatar
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25 votes
8 answers
29k views

Would it help if you jump inside a free falling elevator?

Imagine you're trapped inside a free falling elevator. Would you decrease your impact impulse by jumping during the fall? When?
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16 votes
3 answers
4k views

Why doesn't gravity speed up light?

We know that gravity speeds up a body; for instance, a meteor which enters the earth gets constantly accelerated up by earth's gravity. And from relativity we know that light bends near a massive body,...
Yashbhatt's user avatar
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10 votes
3 answers
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How can an object's instantaneous speed be zero and it's instantaneous acceleration be nonzero?

I'm studying for my upcoming physics course and ran across this concept - I'd love an explanation.
anjunatl's user avatar
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8 votes
3 answers
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Integrating radial free fall in Newtonian gravity [duplicate]

I thought this would be a simple question, but I'm having trouble figuring it out. Not a homework assignment btw. I am a physics student and am just genuinely interested in physics problems involving ...
Kam's user avatar
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25 votes
4 answers
11k views

Is there a maximum possible acceleration? [closed]

I'm thinking equivalence principle, possibilities of unbounded space-time curvature, quantum gravity.
Nigel Seel's user avatar
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3 votes
4 answers
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Why acceleration comes to be different when using $F=ma$ and when using $\tau = I \alpha $?

Consider a Disc of mass $M$ and radius $R$, I applied force $F$ tangentially on it. Now using $F=Ma$ , acceleration comes up to $$a=F/M$$ Now, let's use the torque equation: Here, the moment of ...
Player Minus One's user avatar
2 votes
1 answer
2k views

Are velocity and acceleration smooth quantities?

My thinking: acceleration corresponds to a force which is instantaneous, so the acceleration of a rigid body can be rather spiky (non-smooth) velocity (angular velocity) describes the ratio of ...
Hello lad's user avatar
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23 votes
4 answers
16k views

Acceleration in special relativity

I am currently studying the motion of relativistic charged particles in electromagnetic fields. More exactly, we first derived the equation of motion in the 4-vector formalism. I was a bit confused ...
Isaac's user avatar
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19 votes
2 answers
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Relativistic centripetal force

The thought randomly occurred to me that a circular particle accelerator would have to exert a lot of force in order to maintain the curvature of the trajectory. Many accelerators move particles at ...
Alan Rominger's user avatar
18 votes
4 answers
4k views

Force as change in momentum vs. change in velocity

Is there ever a situation where the distinction between $F = m \frac{dv}{dt}$ and $F = \frac{dp}{dt}$ is important? I can't think of a situation where one is true and not the other (assuming only ...
DilithiumMatrix's user avatar
12 votes
7 answers
7k views

Why is $F=ma$? Is there a straightforward reason?

Why is force = mass $\times$ acceleration? I have searched in many sites but didn't actually get at it. Simply I want to know that if a mass in space moves (gains velocity thus further accelerates), ...
Lucius Pertis's user avatar
16 votes
7 answers
11k views

Is acceleration relative?

A while back in my Dynamics & Relativity lectures my lecturer mentioned that an object need not be accelerating relative to anything - he said it makes sense for an object to just be accelerating. ...
user27182's user avatar
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10 votes
3 answers
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The two causes for the factor 2 in Coriolis effect

While reading this document on Coriolis effect http://empslocal.ex.ac.uk/people/staff/gv219/classics.d/Persson98.pdf, I saw the followig sentence Two kinematic effects each contribute half of the ...
Sørën's user avatar
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7 votes
3 answers
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Calculating gravity when taking into account the change of gravitational force

This is a problem that has bothered me for a couple of weeks now, and I can't seem to wrap my head around it and understand it. Let's say we have a planet with a mass of $m$. We also have an object of ...
Freyja's user avatar
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12 votes
4 answers
2k views

Which clock is the fastest inside an accelerating body?

The picture shows an accelerating spaceship with two clocks inside it. It is so far away from all other bodys that gravity is of no importance. Will the bottommost clock be slower than the topmost ...
Friend of Kim's user avatar
10 votes
6 answers
3k views

Physical intuition for higher order derivatives

Could somebody give me an intuitive physical interpretation of higher order derivatives (from 2 and so on), that is not related to position - velocity - acceleration - jerk - etc?
user680111's user avatar
0 votes
2 answers
2k views

Tangential acceleration in circular motion?

A lot of my problems have objects moving in circular paths with tangential and normal components of acceleration. If the tangential component is non-zero though, the speed is changing so the radius ...
dfg's user avatar
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42 votes
5 answers
21k views

Slinky base does not immediately fall due to gravity

Why does the base of this slinky not fall immediately to gravity? My guess is tension in the springs is a force > mass*gravity but even then it is dumbfounding.
Smoke Trees's user avatar
41 votes
5 answers
32k views

Why do heavier objects fall faster in air?

We all know that in an idealised world all objects accelerate at the same rate when dropped regardless of their mass. We also know that in reality (or more accurately, in air) a lead feather falls ...
Simd's user avatar
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21 votes
4 answers
26k views

Does velocity or acceleration cause time dilation?

What causes time dilation? Acceleration or velocity? I've seen multiple comments on this forum that assert velocity is the cause, but that doesn't seem right to me. You can't have velocity without ...
Jay's user avatar
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21 votes
8 answers
111k views

A simple derivation of the Centripetal Acceleration Formula?

Could someone show me a simple and intuitive derivation of the Centripetal Acceleration Formula $a=v^2/r$, preferably one that does not involve calculus or advanced trigonometry?
Conceptuality's user avatar
13 votes
2 answers
15k views

Why do accelerating electrons emit radiation?

I know how you can emit light with an alternating current, running back and forth, creating an electric field in addition to the magnetic field. But why does an electron emit light when it gets ...
user avatar
13 votes
5 answers
9k views

Is acceleration an absolute quantity?

I would like to know if acceleration is an absolute quantity, and if so why?
tsudot's user avatar
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1 vote
1 answer
2k views

Newtons Cradle, Collision Theory

It has come to the point in my computing program now where I have 5 swinging pendulums that are all modified at once by slider values. These values are drawn onto the from and passed through the class ...
Corey Ford's user avatar
1 vote
3 answers
3k views

Why normal acceleration doesn't bring a change in speed?

Suppose There's a particle of mass m moving with speed $v_{0}$, at certain moment a force starts acting on it (centripetal force) and it start uniform circular motion Now every other reference states ...
Xasel's user avatar
  • 373
23 votes
7 answers
10k views

Can an object *immediately* start moving at a high velocity?

What I mean is, suppose a ball is fired from a cannon. Suppose the ball is moving at 100 m/s in the first second. Would the ball have started from 1m/s to 2m/s and gradually arrived at 100m/s? And is ...
Siddharth Jossy's user avatar
20 votes
2 answers
2k views

Does an accelerating electric dipole radiate?

For such a simple question I'm finding it remarkably hard to get a definitive answer. Googling has not helped me. Consider an ideal electric dipole that is constant i.e. neither its magnitude nor ...
John Rennie's user avatar
16 votes
3 answers
3k views

How does anything move? [duplicate]

So in order for two things $A$ and $B$ to move apart, for example, relative to each other, $B$ can be set into motion away from $A$. This means that we have to increase $B$'s velocity and therefore ...
under_the_sea_salad's user avatar
13 votes
11 answers
5k views

Does force cause acceleration or acceleration cause force?

I am currently studying advanced mechanics (meaning I do have an introduction in mechanics). I know the question is a bit weird (actually a lot). My question is: "Is it the acceleration which ...
Charu _Bamble's user avatar
10 votes
3 answers
553 views

How to describe arbitrary accelerations in special relativity

Describing acceleration in special relativity is in principle straightforward, and for simple cases the resulting transformations are simple. Examples include circular motion and constant acceleration ...
John Rennie's user avatar
9 votes
5 answers
8k views

Is there a scalar acceleration?

The magnitude of Velocity is simply Speed. On the other hand, the magnitude of Displacement seems to be a simpler idea than Distance. And the magnitude of Acceleration is not the change of Speed over ...
clausvalca226's user avatar
4 votes
7 answers
629 views

Type of force of $m\vec{a}$

As there are types of forces such as Normal, Tensional, Gravitational, etc. Suppose a block of mass $m$ kept on a table and a man is pushing it and a acceleration $\vec{a}$ is produced. Is $m\vec{a}$ ...
Shreyansh Kuntal's user avatar
2 votes
3 answers
5k views

Classical car collision [duplicate]

I have a very confusing discussion with a friend of mine. 2 cars ($car_a$ and $car_b$) of the same mass $m$ are on a collision course. Both cars travel at $50_\frac{km}{h}$ towards each other. They ...
Madara's Ghost's user avatar
30 votes
3 answers
3k views

How is the energy loss by an accelerating charge expressed in the equations of motion?

I understand how, and why, an accelerating charge emits radiation, and loses energy in the process, as well as the Larmor formula for the power, and its derivation. However, in classical mechanics, ...
roymend's user avatar
  • 812
27 votes
8 answers
22k views

Why doesn't the Earth accelerate towards us?

According to Newton's third law of motion that states that every action has an equal and opposite reaction. So, if the Earth exerts a gravitational pull on us (people) then even we should exert a ...
whae's user avatar
  • 1,033
15 votes
3 answers
615 views

Can the question of a gravitationally accelerated charge radiation be tested experimentally?

I know that the question of radiation from a gravitationally accelerated charge has been discussed extensively at Does a charged particle accelerating in a gravitational field radiate?. Yet the ...
Philipp's user avatar
  • 166
11 votes
3 answers
917 views

Regarding Goldstein's claim that $\mathbf{F} = \dot{\mathbf{p}}$

From Goldstein: ... The mechanics of the particle is contained in Newton's second law of motion, which states that there exist frames of reference in which the motion of the particle is described ...
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