# Questions tagged [acceleration]

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

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### Rotational analogue of Newton's 2nd law

If we are writing torque equation about general point what points must be taken into account for getting the correct result. Also If that general point is accelerated then how do we deal with this. ...
44 views

### Acceleration of The Centre of Mass of A Rod

The acceleration a of the center of mass of a system is equal to F/M, where F is the net external force and M is the total mass of all the particles of the system, or at least that is my current ...
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### Do variations of the Earth's magnetic field affect gravitational acceleration at Earth's surface, and if yes, by how much?

The Earth's magnetic field varies with time over geological time scales (we have phenomena such as pole inversion). Can this affect the acceleration of gravity at Earth's surface? I would think that ...
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### What would happen if I used a jet pack that accelerates at $g$ but always upward?

I'm trying to imagine what would happens if gravity is cancelled. I assume that without air, if the effect of gravity were to disappear I would fly off Earth on a tangential line. But with the air ...
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### Does a charge in a gravitational field make a magnetic field?

I know that general relativity unifies the electric charge with the magnetic field via relative motion. So if I accelerate a charge then anyone in another inertial frame will see a magnetic field. ...
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### How and why does momentum get transferred? [closed]

Let us imagine an isolated system and there are two objects of whatever masses and size. Let one object move towards the other object with constant velocity. We know, that when they collide, the ...
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### Can an object have constant speed and tangential acceleration without undergoing circular motion?

Is it possible for an object to be moving with constant speed and a constant magnitude of acceleration tangent to this velocity but NOT move in a circular path? If there are other situations could I ...
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### Acceleration downhill, fastest trajectory for a ball

Given 3 ways of going downhill, like in this image: Would a ball behave like that in real life? Intuitively, it makes no sense. The shortest path here is not the fastest. Any hints to the math ...
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### Special Relativity for Synchrotron Radiation

For the last few hours, I tried to solve an exercise about synchrotron radiation but can't get to a solution. I think there are some concepts about special relativity that I didn't understand during ...
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### Instantaneous changes in acceleration

These are very simple looking graphs. What I don’t understand is (I’m talking of the highlighted text in blue at the bottom), it says such instantaneous changes in acceleration can not occur in ...
648 views

### Can you jump higher if you run? If so, why? (High jumping)

I have often wondered why high jumpers can jump higher if you run. The way I see it is that you only build up horizontal speed, and since you're running on a plane, I cannot see how this speed can be ...
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### Why is acceleration variable in uniform circular motion?

Acceleration is the rate of change of velocity. In the uniform circular motion the acceleration is produced due to change of direction of the velocity(the magnitude remains same). The direction is ...
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### Reference frames and Newton’s second law

I have an understanding Issue. We were told that apparent weightlessness was due to the absence of Normal Reaction force.The example chosen was a man in a lift...the latter moving with different ...
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### Einstein's Elevator - Constant acceleration eventually reaches $c$. Can't that be used to detect gravity vs acceleration?

Objects with mass that continuously accelerate will eventually approach $c$, but cannot exceed it. So if I find myself in an elevator, unable to determine if I'm in a uniform gravitational field or ...
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### Fastest hyperloop-like vehicle which a human could endure [closed]

I'm currently writing on a science-fiction novel where a transportation system like the hyperloop has been built. Now, I'm wondering how fast I can make this. Since the plot takes place on many ...
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### Torque, Angular Acceleration and Linear Acceleration

We know that we torque is applied, it cause an angular acceleration in the rotating body similar to what a force does to a body moving on a straight line. But my question is, Does Torque affect the ...
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### Calculation of speed from accelerometer data

I am trying to use my accelerometer on my mobile device fitness band to find the speed of walking and running. I conducted my experiment of walking and running on treadmill where I asked a person to ...
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### How did Henry Kater measure distances down one part in $10^5$?

Wikipedia says that in 1817, Henry Kater was able to measure distances accurately enough to get at least five significant figures in a measurement of $g,$ suggesting that he could measure a distances ...
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### Acceleration interpretation in accelerated frames in general relativity

I would like to know whether my physical interpretation of some dynamics in accelerated frames is correct. In a frame with acceleration $a$ we have the metric $$ds^2 = (1+ax)^2 dt^2 - dx^2$$ The ...
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### Does the rope stretch when the pulley of Atwood's machine is accelerated?

Let's say I've an Atwood's machine in which I have two point masses which are different. Now, when I accelerate the pulley, the two masses accelerate at a different rate which can be shown by ...
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### If there was but one object in the universe, can it be accelerating or not accelerating?

If there is only a single (material) object in the universe does it still make sense to speak of it as accelerating or not accelerating? I believe it might be an equivalent question to ask whether it ...
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### Can we divide a vector by another vector? How about this: $a = vdv/dx?$

My physics teacher told us that we can’t divide vectors, that vector division has no physical meaning or significance. How about this: $$a = vdv/dx.$$ It says acceleration vector equals velocity (as ...
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### Effect on speed when decreasing the magnitude of acceleration

I'm struggling to come up with an answer to the following situation and question: "Suppose you are driving your car along a straight road in the positive direction and are speeding up (increasing ...
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### Acceleration formula derivation (newtonian physics) [closed]

Acceleration has a simple equation in physics: $$a = \frac{(v-u)}{t}$$ (should be $\Delta v / \Delta t$) Both $v$ and $u$ have $s/t$ as their formula. So, dividing twice by time gives time squared, ...
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### Lifting an Object On A Scale

Let's say hypothetically that I'm standing on a scale while holding an object with some mass. If I accelerate the mass upwards (with my hands), will the reading on the scale increase? I've been ...
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### How one can actually define an infinite family of Momentarily Comoving Reference Frames (MCRF)?

In Griffith's General Relativity there is the following line: An accelerated particle has no inertial frame in which it is always at rest. However, there is an inertial frame which momentarily has ...
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### Possible paradox relating to acceleration, velocity, and work

I recently encountered a question that made me think of this "paradox": Imagine the following situation: There are two forces: Force 1 and Force 2. They accelerate a mass $m$ from the same initial ...
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### How force is equal to the product of mass and instantaneous acceleration?

$$\vec{F}=m\vec{a}$$ Suppose that an object of some mass was constantly accelerating ($\vec{a} \neq 0$) through sometime interval. With no doubt, the object had an instantaneous acceleration at any ...
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### Constant acceleration space travel: velocity relative to the Earth? [duplicate]

Suppose we are in a spacecraft that is moving away from the Earth along a straight line with a constant acceleration of $1G$, and that this acceleration can be sustained indefinitely. Accelerating at ...
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### The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than [closed]

The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than 250 m/s². If you are in an auto- mobile accident with an initial speed of 105 ...
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### Phone accelerometer - formula to calculate angular gravity

I am taking readings from the accelerometer of a smartphone and want to account for gravity. My device reports residual gravity as "10g" (device stationary, screen facing up). As the angle of the ...
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### How to Find Jerk from Discrete Velocity Data?

I have measured the velocity of an object at discrete intervals. I want to find the corresponding acceleration and jerk of the object. How do I do this with discrete values rather than continuous ...
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### Newtonian Mechanics cannot be applied in non-inertial frame of reference then how can we apply formula for normal force in an accelerating elevator?

In my physics book there is a diagram in which a block is placed on a table. The table is exerting an upward force $F_n$ (normal force) on the block and there is a downward force $F_g$ (...
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### 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 ...
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### What would the position vs. time graph look like if the velocity vs. time graph was a curve?

In my physics class we are learning about velocity vs. time graphs and position vs. time graphs for an object. We have learned that if the object is moving with constant velocity (this would be a ...
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### Angular Acceleration of a uniform solid sphere in a hemispherical bowl

Consider a ball of radius $r$ moving(surfaces are frictionless) inside a hemispherical bowl of radius $R$ and mass $m$. Now if I were to find the angular acceleration ($α$ of the ball I analyse the ...
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### How to know which constant acceleration equation to use? [closed]

The question I'm working on: This is the answer: For (b), I just want to know why we use ((v+u)/2)t) to find the displacement of the mailbag. It is clearly a free falling object that has ...
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### Average Velocity Question (isolation?)

So there is this question i've been having trouble with for the past hour. It involved a child going down a ramp on a sled at and angle theta with a total system of mass. accelerates down a hill of ...
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### Why acceleration comes to be diffrent when using $F=ma$ and when using $\tau = I \alpha$? [closed]

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 ...
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### Acceleration: $G$ and $G$s difference

In some literature the acceleration is stated in Gs units. For example, "All structures shall be built to survive 15 Gs of launch acceleration". However, g-force sometime also stated in G units ...
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### Is the acceleration of a rotating body always it's centripetal component? [closed]

For constant circular motion where a rotating mass accelerates angularly. Would the linear acceleration of the rotating mass always be equal to its centripetal acceleration e.g. The earth's ...
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### How to get the acceleration of a rotating mass from it's centrifugal and centripetal components

Suppose I pull out a rope and rotate a small mass as in the diagram with its speed constantly increasing Where: $Q_1$ is the path of the rotating mass $m$ $Q_0$ is the center of the rotating mass ...
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### Does light get acceleration due to gravity? [duplicate]

When an object, say a ball, is attracted by the black hole it gets acceleration due to gravity. Suppose light is moving towards the black hole vertical to it... then does it gain acceleration due to ...
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### How to determine the direction of a vector?

I have been learning about vectors and acceleration recently and I still don't understand how to determine the direction of a vector. For instance, if we consider a freely falling particle and ...
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### Gravity / Rate Of Fall Paradox on Moon Earth

It is well known that the rate of fall in the vacuum on the Earth is equal for all bodies, e.g. a feather and a gold bar, so on the moon as well. However, the moon has according to less mass also less ...
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### Gravity, falling bodies, and the equivalence principle

Why is that bodies in a box accelerating uniformally in space that is sufficiently removed from gravitational fields fall identically to bodies in a box located in a homogeneous gravitational field (e....
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### How did Einstein use the conclusions of special relativity to reach the equivalence principle (using the Elevator thought experiment)?

Could someone please explain how Einstein used the Elevator thought experiment and the principles of special relativity to conclude that uniform accelerates creates uniform gravitational field (...
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### Work done in accelerating an object in circular motion

In a hammer throw competition, an athlete spins a “hammer” before releasing it. The “hammer” used in this sport is a metal ball of mass 𝑀 = 8 kg and diameter 𝐷 = 30cm, which is attached to a ...