Questions tagged [acceleration]
The rate of change of velocity of a body per unit of time.
414
questions
267
votes
11
answers
65k
views
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 ...
- 2,908
11
votes
3
answers
2k
views
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 $$\vec a=\...
- 1,770
27
votes
7
answers
233k
views
Why do two bodies of different masses fall at the same rate (in the absence of air resistance)?
I'm far from being a physics expert and figured this would be a good place to ask a beginner question that has been confusing me for some time.
According to Galileo, two bodies of different masses, ...
- 389
74
votes
7
answers
10k
views
Does a charged particle accelerating in a gravitational field radiate?
A charged particle undergoing an acceleration radiates photons.
Let's consider a charge in a freely falling frame of reference.
In such a frame, the local gravitational field is necessarily zero, ...
- 2,505
100
votes
5
answers
101k
views
How and why do accelerating charges radiate electromagnetic radiation?
Let's consider it case by case:
Case 1: Charged particle is at rest. It has an electric field around it. No problem. That is its property.
Case 2: Charged particle started moving (it's accelerating)....
- 7,145
11
votes
6
answers
15k
views
Do photons have acceleration?
Photons travel at the fastest speed in our universe, the speed of light.
Do photons have acceleration?
- 1,007
60
votes
7
answers
11k
views
Does a constantly accelerating charged particle emit EM radiation or not?
The Abraham-Lorentz force gives the recoil force, $\mathbf{F_{rad}}$, back on a charged particle $q$ when it emits electromagnetic radiation. It is given by:
$$\mathbf{F_{rad}} = \frac{q^2}{6\pi \...
- 5,507
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 ...
- 1,515
61
votes
4
answers
19k
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 ...
- 715
65
votes
10
answers
39k
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 ...
- 753
19
votes
5
answers
126k
views
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 ...
- 1,507
5
votes
1
answer
7k
views
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, $r$ ...
- 657
25
votes
8
answers
28k
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?
user145
15
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,...
- 1,794
10
votes
3
answers
59k
views
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.
- 203
8
votes
3
answers
6k
views
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 ...
- 93
3
votes
4
answers
1k
views
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 ...
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 ...
- 123
23
votes
4
answers
15k
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 ...
- 2,840
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 ...
- 14k
12
votes
7
answers
6k
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), ...
- 147
25
votes
4
answers
10k
views
Is there a maximum possible acceleration? [closed]
I'm thinking equivalence principle, possibilities of unbounded space-time curvature, quantum gravity.
- 3,316
14
votes
6
answers
10k
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. ...
- 1,619
7
votes
3
answers
10k
views
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 ...
- 164
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 ...
- 495
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?
- 202
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 ...
- 1,991
41
votes
5
answers
31k
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 ...
- 1,131
21
votes
4
answers
24k
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 ...
- 663
19
votes
8
answers
100k
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?
- 353
17
votes
2
answers
12k
views
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 ...
- 20.9k
13
votes
5
answers
8k
views
Is acceleration an absolute quantity?
I would like to know if acceleration is an absolute quantity, and if so why?
- 971
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 ...
user24082
10
votes
3
answers
3k
views
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 ...
- 2,517
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 ...
- 113
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 ...
- 373
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.
- 423
19
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 ...
- 349k
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 ...
10
votes
3
answers
521
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 ...
- 349k
4
votes
7
answers
599
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 $m\vec{a}$ ...
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 ...
- 223
29
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, ...
- 770
27
votes
8
answers
21k
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 ...
- 1,023
15
votes
3
answers
583
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 ...
- 166
11
votes
3
answers
843
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 ...
user113773
9
votes
4
answers
7k
views
Is there a scalar acceleration?
Distance is paired with Displacement and it seems to be a bigger idea than just the magnitude of Displacement. Speed is paired with Velocity. I have always thought that there is not such pairing with ...
9
votes
3
answers
2k
views
If $F=ma$, how can we experience both gravity and a normal force even though we are not accelerating?
As I sit in my chair, I experience a gravitational force pushing me into the chair and I'm also experiencing the normal force of the chair pushing back at me so I don't fall. According to Newton's ...
- 121
8
votes
6
answers
3k
views
Why are position and velocity enough for prediction and acceleration is unnecessary?
In classical mechanics, if you take a snapshot and get the momentary positions and velocities of all particles in a system, you can derive all past and future paths of the particles. It doesn't seem ...
- 885
7
votes
1
answer
1k
views
Does an object creates gravitational waves when only accelerating in one direction?
I know from reading about the gravitational waves detected by Ligo, that when an object has angular acceleration, it produces gravitational waves.
I'm wondering if an object creates gravitational ...
user109792