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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Deriving normal acceleration in a uniform circular motion using limits [closed]

I came up with the following "derivation" of the centripetal acceleration formula, $ a=\frac{v^2}{r}.$ It's obviously wrong, but I can't find the error. Consider the following figure: Let $...
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Relativistic Rocket with Constant Acceleration [duplicate]

How long does it take to (constantly) accelerate to a relativistic velocity? Inspiration from [0] and [1]. Assume you are sitting in a spaceship. To make you feel home, the spaceship accelerates such ...
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Can imaginary (illusionary) forces cause acceleration, and what exactly are they?

We might be aware of illusion forces such as centrifugal force that doesn't really exist but we feel the force for sure, how is that exactly possible? I don't yet know much in Physics but does any ...
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What's the difference between using $a=(v2-v1)/t$ and $s=u\cdot t+1/2\cdot a\cdot t^2$? [closed]

I have a coilgun shooting a projectile at initial velocity=0. We tracked the final velocity by dividing distance (0.5m) by time (0.13s) from exit of coilgun to impact 0.5m away with a camera. So: v2=0....
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The meaning of negative sign in vectors?

if the velocity vector $\overrightarrow{v}=v\widehat{i}$ ,, we define the accelration vector as it's the time derivative of the velocity vector $\overrightarrow{a}=(\frac{dv }{dt})\...
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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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3 answers
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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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2 answers
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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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6 votes
1 answer
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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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2 answers
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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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2 answers
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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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3 answers
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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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What happens to the motion of the body if acceleration equal zero? [closed]

$If$ the body moves with $variable$ velocity and $variable$ acceleration ,but at a certain instant the $acceleration$ was zero then we can say at this instant the body moves with constant $velocity$ $?...
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-1 votes
1 answer
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Distance contraction and acceleration [closed]

I'm trying to understand length contraction. I've created a diagram with three examples. I'm wondering if my diagram is correct. According to this diagram, when you accelerate towards an object, the ...
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1 vote
2 answers
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Length contraction and acceleration in opposite directions

If you accelerate in a direction, objects in front and behind you get closer relative to you. If you then accelerate again in the opposite direction, the same thing happens, which leads to a ...
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1 vote
1 answer
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Ball attached to string snaps in decelerating car

A ball hanging from the ceiling in a decelerating car will make an angle. What happens if the string snaps while the car is decelerating? As gravity is the only force acting on the ball after the ...
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1 answer
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Splitting gravity along $x$, $y$, and $z$ axes

For my diploma project, I am building a posture correcting wearable, being able also to recognize some activities such as walking/running, climbing stairs, etc., and for this, I am using some ...
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4 votes
4 answers
131 views

With how many Newtons of force is the universe expanding?

The universe is expanding at an accelerating rate. They key word here is "accelerating". Meaning that there is an equivalent "force" (in Newtons) that would cause that same ...
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Does Diamagnetism actually lessen G forces?

Example: Astronauts are pinned to their seats by 3gs during takeoff. If there were a sufficiently strong diamagnetic field, would the g-forces felt by the astronauts be lessened, or would they simply ...
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1 vote
3 answers
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Meaning of "$=$" in $\vec{F}=m\vec{a}$ (for example)

I don't understand how the two could really be one and the same. E.g. we can exert forces $\vec{F}$ and $-\vec{F}$ on a body and it's acceleration will not change. I don't think it makes sense to say ...
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If I hang from the ceiling of the elevator which is falling freely then will I experience weightlessness?

We all know that while the lift (or elevator) is accelerating downwards we feel less weight, now suppose I hang from the ceiling with the help of a stick in some cavity of the ceiling itself, then ...
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1 answer
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What would happen if when falling down you get pushed up?

I know it will be a weird question, but im not a physics well informed person and I had this unsolved question for long time. What would happen if lets say you are falling with someone else from ...
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Layman question about relativistic motion

I hope I can convey my question in a reasonable way: I know that if Alice is moving towards Bob at $0.75\,c$ and Bob does the same towards Alice, then to calculate how each one of them measures their ...
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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?
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