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

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75
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8answers
15k 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 ...
4
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6answers
3k views

Do photons have acceleration?

Photons travels with the largest speed in our universe, the speed of light. Do photons have acceleration?
5
votes
5answers
2k 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, ...
3
votes
2answers
1k views

Classical car collision

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 ...
1
vote
1answer
375 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 ...
42
votes
4answers
7k 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 ...
7
votes
4answers
661 views

Integrating radial free fall in Newtonian gravity

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 ...
2
votes
1answer
1k views

Force on rope with accelerating mass on pulley

I have a pretty basic pulley problem where I lack the right start. A child sits on a seat which is held by a rope going to a cable roll (attached to a tree) and back into the kid's hands. When it ...
2
votes
4answers
8k views

Free falling of object with no air resistance

Why does an object with smaller mass hits the ground at same time compared to object with greater mass? I understand the acceleration due to gravity of earth will be same but won't the object with ...
2
votes
1answer
97 views

How to find equation of motion for this trajectory? - object leaves curved ramp at a given velocity [closed]

Here is the sketch: The sketch is supposed to be side-view of the path of the object. The following values are known: $r$ - radius of the circle that describes the path AB of the object $a$ - ...
13
votes
1answer
1k views

What came first, Rice Crispy or “Snap,” “Crackle,” and “Pop”? [closed]

The fourth, fifth, and sixth derivatives of position are called "Snap" "Crackle" and "Pop". What came first, the rice crispy characters, or the physics units?
7
votes
5answers
12k 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 ...
12
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5answers
3k 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 ...
11
votes
1answer
782 views

How do I calculate the (apparent) gravitational pull with General Relativity?

Assume a static metric with (known) components $g_{\mu\nu}$. I'd like to know what is the gravitational pull $g$ of a test particle placed on an arbitrary point $X$. The gravitational pull being ...
8
votes
2answers
2k 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 ...
6
votes
4answers
1k 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. ...
4
votes
4answers
1k views

Is acceleration an absolute quantity?

I would like to know if acceleration is an absolute quantity, and if so why?
7
votes
3answers
576 views

Dark Energy / Accelerating universe: naive question

Folks, I have a naive question regarding the subject of dark energy and an accelerating universe: From what I understand/read, it seems that the further we look out into deep space, the faster the ...
4
votes
2answers
3k 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.
1
vote
2answers
174 views

How an accelerated object sees another accelerated body in special relativity?

Assume two objects are moving with a constant acceleration $a_1$ and $a_2$, which are the measured accelerations by respective object (or constant force being applied to each of the objects). My ...
12
votes
7answers
4k 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?
3
votes
1answer
1k 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 $$F = \dfrac{G \cdot m_1 \cdot m_2}{r^2} $$ So, as the body falls ...
2
votes
1answer
652 views

Kinematics with non constant acceleration

A particle experiences an acceleration described by $$ a=kx^{-2} $$ where x is the displacement from the origin and k is an arbitrary constant. To what value does the velocity v of the particle ...
1
vote
0answers
39 views

Calculate the acceleration of the trailing muon bunch

Two separate suitably short but intense bunches of muons, "A" and "B", are both supposed to be constantly accelerating (in an otherwise sufficiently flat region) with constant proper acceleration ...
1
vote
1answer
243 views

Accelerating elevator?

If your in an elevator accelerating downwards faster than gravity, would you be pushed up to the ceiling? Since gravity cannot match the acceleration of the elevator, you're wouldn't be able to move ...
14
votes
2answers
344 views

Do accelerated charges radiate or not?

This questions has been asked all over the net (here included) but I can't find a satisfactory answer or discussion. Some say it does not radiate if the acceleration is caused by a uniform gravity ...
15
votes
7answers
358 views

Is there a limit to acceleration?

As we all know the speed of light is the limit at which energy/matter can travel through our universe. My question being: is there a similar limit for acceleration? Is there a limit to how quickly ...
2
votes
1answer
99 views

When photons are emitted, do they accelerate to reach the speed of light? [duplicate]

Photons are considered mass-less particle with a specific velocity but according to the electromagnetic theory, a photon is considered to have both energy and momentum. So what happen when they are ...
6
votes
1answer
718 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.
6
votes
8answers
2k views

Can you completely explain acceleration to me?

I understand what acceleration is, and I know the formula, and I understand it's a vector. I just don't understand how the equation works exactly. I'm kind of picky, I know, but bear with me. ...
5
votes
3answers
3k views

Convert acceleration as a function of position to acceleration as a function of time?

Suppose I have acceleration defined as a function of position, $a(x)$. How to convert it into a function of time $a(t)$? Please give an example for the case $a(x)= \frac{x}{s^2}$.
4
votes
5answers
775 views

Why doesn't an electron accelerate in a circuit?

Why don't electrons accelerate when a voltage is applied between two points in in a circuit? All the textbooks I've referred conveyed the meaning that when an electron traveled from negative potential ...
3
votes
2answers
1k views

Formulas for ball rolling in a bowl?

I'm developing a program where I've a ball/sphere rolling in a bowl from the side at top, till the center at bottom, and I'm trying to get the formulas for: The rotation angle and the position of ...
2
votes
3answers
1k views

What is the velocity area method for estimating the flow of water?

Can anyone explain to me what the Velocity Area method for measuring river or water flow is? My guess is that the product of the cross sectional area and the velocity of water flowing in a pipe is ...
23
votes
6answers
3k 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 ...
5
votes
2answers
555 views

relativistic acceleration equation

A Starship is going to accelerate from 0 to some final four-velocity, but it cannot accelerate faster than $g_M$, otherwise it will crush the astronauts. what is the appropiate equation to constraint ...
3
votes
2answers
1k views

Fictitious forces confusion

I have a hard time understanding the subject of fictitious forces. Let's discuss a few examples: 1) I'm sitting inside a vehicle which is accelerating in a straight line. I feel like someone is ...
3
votes
5answers
3k views

If a space ship accelerated constantly, would its astronauts constantly feel the forward movement?

I know that if a space ship suddenly traveled very fast, its astronauts would be fly against the back wall, potentially getting hurt. If the space ship suddenly stopped, they would also fly against ...
3
votes
6answers
4k views

Ion Drive Propulsion Top Speed

I would like to know if there is some formula / graph which would provide / show the efficiency of a certain type of propeller in space. Specifically, I'm interested in the acceleration attainable at ...
2
votes
2answers
198 views

Understanding bending light beam perpendicular to motion

I'm just reading a book about gravity. An example it gives is a spaceship accelerating. A beam of light travelling at right angles to the direction of movement of the spaceship enters it via a small ...
1
vote
2answers
191 views

Do heavier objects fall faster? [duplicate]

This question has been asked multiple times here and all over the internet yet I can't find a conclusive answer: Some claim that heavier objects do fall faster: Don't heavier objects actually fall ...
1
vote
0answers
39 views

Acceleration by spherical particles (micron-scale) by an external force

I am looking for an expression for the velocity of a micron sized (1 - 10 micron diameter) sized particles under accelerating forces. I have aerosols in mind. This is what I have in mind The ...
1
vote
2answers
304 views

Using acceleration to plot position

Sorry if this question is dumb, and I know is physics 101, but I'm not that good with physics. I'm writing an iPhone program that by collecting the acceleration data of the device tries to replicate ...
0
votes
1answer
335 views

Accelerated liquid in a U-tube

Consider a U-tube containing some liquid. The two ends of the tube are connected to closed volumes of air with different initial pressures, such that there is some difference in the liquid levels ...
7
votes
3answers
770 views

In mechanics, is shock really better expressed as jerk instead of acceleration?

Some expensive electronics or mechanical devices are designed to be shock-resistant. However, the manufacturers often market the level of shock-resistance in units of g-force (I know g-force is really ...
3
votes
2answers
144 views

Proper Time with a non-zero Initial Velocity

I have a question regarding how to find the proper time for a body with an initial velocity to slow down to 0. For example, the equation I have been working with looks like: $$\int^\tau_0 ...
3
votes
1answer
287 views

What are the general relativity equations for relativistic constant acceleration?

At constant acceleration in special relativity, the time differs for a stationary observer and the astronaut. see the following article for an in-depth explanation: Relativistic Rocket However, when ...
3
votes
2answers
919 views

Does a moving escalator make it easier to walk up the steps?

I was discussing with my colleagues why it feels easier to walk up an escalator when it is moving. My natural assumption was that the movement of the escalator imparts some extra acceleration on the ...
2
votes
2answers
77 views

How do we know gravity isn't acceleration? [closed]

If an accelerometer sitting at rest on the earths surface measures 1 G of acceleration upward. How do we know "space" (the reference) isn't rushing down into the earth. I mean experimentally that's ...
2
votes
1answer
323 views

Derivation of hyperbolic motion in Special Relativity

My question pertains to the equation of hyperbolic motion in special relativity: $$x^{2} - c^{2}t^{2} = c^{4}/\alpha^{2}.$$ As far as I am aware, this equation is the key to calculating coordinate ...