# Questions tagged [acceleration]

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

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### What is the shape of the Rindler horizon?

Consider a relativistically accelerating body, it is said that from its frame of reference there would appear to be a Rindler horizon at a distance $d =\frac{c^2}{a}$. My question is about the body's ...
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### The value of $g$ in free fall motion on earth

When we release a heavy body from a height to earth. We get the value of $g=9.8 \ ms^{-2}$. Now, I'm confused about what it means. For example, does it mean that the body's speed increases to $9.8$ ...
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### How does negative velocity and positive acceleration exactly and vice versa slow down objects?

I am kinda confused how does negative velocity(-v) and positive acceleration(+a) exactly and vice versa slow down objects? i have a thought about it please let me know if i am correct. according to ...
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### What exactly is happening to acceleration when direction changes?

As direction changes i know that acceleration occurs but what exactly is happening to it, is it increasing acceleration, decreasing acceleration, constant acceleration, negative acceleration or ...
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### An object falling from very far would have varying acceleration, how can that be accounted for?

I want to have a function that describes where a falling object is. Like this one: h(t) = -g*t²/2 But this one is for the usual close to the surface case, where there is no variation of gravity due to ...
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### How to find the direction of acceleration if an object is changing its direction of velocity but not magnitude then how we can find the direction

I am new at this topic so please do mind if my question doest make sense to you.I am trying to find out that what will be the direction of acceleration if object changes Direction of velocity but not ...
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### The utility of HorsePower vs Torque [closed]

All vehicles have only 1 gear Final-drives allow peak RPM (HP) at red line = 35 MPH Wheel-sizes are equal Tires have perfect traction (yet, no rolling resistance, etc) Goal: isolate all variables ...
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### Special relativity and acceleration of an object falling in a direction perpendicular to the direction of motion

So I'm redoing special relativity because I want to start GR and I thought it might help make the learning somewhat easier, I was doing some SR problems and this thought came to me. Imagine a train ...
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### Confusion regarding pseudo force

I have been taught that a pseudo force is a force that appears to act on a mass whose motion is being described using a non-inertial frame of reference I have also been taught that pseudo force = - (...
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### If An Instantaneous Force Causes A Charged Particle To Briefly Accelerate, Does Self-inductance Decelerate It?

Consider the following example: A charged particle initially at rest briefly accelerates in the forward direction due to an initial force. At this point the particle is carried forward only by inertia,...
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### How effective would a liquid inertial dampener be against mass acceleration

I have heard that a method of inertial dampening is to submerge a person in a liquid as buoyant as them. But I could not find any specific numbers or calculations for this. Example, is there a limit ...
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### Measuring the curvature of the Earth using a mobile phone accelerometer + gyroscope

Suppose that you were on the surface of a sphere which is perfectly level everywhere. You are in a car or a plane, and you have a mobile phone with a gyroscope and an accelerometer that give a steady ...
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### Calculate Speed From An Accelerometer to get meters per second

We are trying to calculate speed in meters per second from an LIS2DH accelerometer. We get ax,ay,az at regular intervals. I have read many posts about calculating the data, and taking an average over ...
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### How do I get the velocity $v$ as a function of position $x$ from the acceleration $a$ as a function of velocity?

Suppose that a particle is moving with a non-constant acceleration on the $x$ axis of $$a(v)= Av^2+Bv+C$$ ($A$, $B$ and $C$ are constants) with an initial velocity of 0 on the x axis and an initial ...
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### Is this expert report wrong about basic kinematics? [closed]

This question is about the application of kinematics in an expert report for Eirikson v. Breton, ABQB 2000 798 (archived), a judgement for a case where a woman was driving a car that was accelerating ...
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### What's the answer to this differential equation of a ball rolling in a semi-circle [closed]

Salute, everyone. Let's assume a ball with a mass $m$ starts falling from the top of a frictionless semi-circular hole in the ground whose radius is $r$. From Newtons second law, we have: $$P_x = ma$$ ...
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### Acceleration of fluid in a magnetohydrodynamics vortex

In the following video we see a mercury vortex done by magnetohydrodynamics: https://youtu.be/au4hbUm4mMo In the following manuscript they say that the fluid will accelerate according to (14) ${}^1$: ...
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### Free Fall and constant acceleration

Although the acceleration of free fall is constant, why don't the distance go like $y = 9.8+4.9= 14.7m$ after 2 seconds, $y= 19.6+14.7 = 34.3m$ after 3 seconds? I think Constant acceleration work like ...
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### Follow-up question on sitting in a train with closed eye, this time only using force sense in a suddenly accelerated train

This very interesting question inspired me to ask a follow-up question. We sit on a comfortable chair in a smoothly rolling train. There are no bumps to be felt. There is no wind to be felt either. We ...
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### Motion of free fall [duplicate]

We know that according to law of free falls object, all bodies fall with the same constant acceleration. But in distance formula ($s = \frac12 gt^2$), why the acceleration is just half?
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### Eyes shut, can a passenger tell if they’re facing the front or rear of the train?

Suppose you’re a passenger sitting in one of the carriages of a train which is travelling at a high, fairly steady speed. Your eyes are shut and you have no recollection of getting on the train or the ...
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### Do tsunamis accelerate on land?

Before they saw the footage, Fritz and Synolakis couldn't understand why so many people had taken photos posing with the wave behind them, out on the open ocean. For some victims, those pictures would ...
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### Trying to understand Newton's Second Law [closed]

If I apply a force on an object at rest and it’s velocity is constant (after force is applied) wouldn’t that mean that the acceleration is 0? Then how would $F=Ma$ make sense? My thinking here is that ...
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### Changing velocity even when acceleration is zero

Consider a particle performing circular motion with position given by $$\vec r=r_0e^{\beta t}\hat r$$ such that $\dot\theta=\omega$, is a constant. The velocity becomes \vec v=\beta r_0e^{\beta t}\...
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### Why do kinematic equations only work with constant acceleration?

People say that the equations are derived assuming a constant acceleration. I just don't see how this is the case. (I am new to calculus.)
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### Why do equation of motion fail to apply in non-inertial frame even after applying pseudo force?

I considered two cars of equal mass moving towards each other with speed 30m/s and 18 m/s respectively and when they are 100 meters apart they both start de accelerating at 6m/s² each. So if we ...
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### How could any frame of reference be inertial?

The image below shows that a bystander watching the merry-go-round is in an inertial frame of reference. However, to nitpick, wouldn't the observer still be accelerating because it's on Earth?
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### Why does Newton's second law involve mass?

Once one has learned of Electromagnetic force, they see that the amount of force experienced by particle given a field is proportional to the particles electric charge. Similar situation the ...
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### Helicopter hover flight question

I'm an avionics technician and I work on helicopters. This week I was trying to explain where comes the lift force to some friends. I'm a self-learner but I have a poor physics school background. I ...
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### Time derivative of unit velocity vector?

Let's say I have some parametric curve describing the evolution of a particle $\mathbf{r}(t)$. The velocity is $\mathbf{v}(t) = d\mathbf{r}/dt$ of course. I am trying to understand what the expression ...
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### Is the deceleration a result of friction, a constant value?

Frictional Force = km, therefore k = a Would this mean that no matter the mass of an object (if they are the same material) They will decelerate at the same speed with friction, therefore if u is the ...
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### If an object is accelerated fast enough, will it become a black hole? [duplicate]

I know that if an object is accelerated, its relativistic mass increases. Does this mean that if it is accelerated fast enough, it will become so massive that it becomes a black hole?
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### Maximum height reached by an object

Here, in the last line, from the formula s is negative, but how can s be negative? Also, should it not be s=u^2/2g instead of s= - u^2/2g?
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### Why is acceleration not usually count as a state? [duplicate]

Position, velocity and acceleration can vary over time. Although only position and velocity are usually count as states of the ODEs. Which makes me wonder why acceleration is not taken as a state?