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24 votes
7 answers
12k views

Zero velocity, zero acceleration?

In one dimension, the acceleration of a particle can be written as: $$a = \frac{dv}{dt} = \frac{dv}{dx} \frac{dx}{dt} = v \frac{dv}{dx}$$ Does this equation imply that if: $$v = 0$$ Then, $$\...
7453rfg's user avatar
  • 383
20 votes
5 answers
131k 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 ...
ben's user avatar
  • 1,517
15 votes
3 answers
4k views

Why does solving the differential equation for circular motion lead to an illogical result?

In uniform circular motion, acceleration is expressed by the equation $$a = \frac{v^2}{r}. $$ But this is a differential equation and solving it gets the result $$v = -\frac{r}{c+t}.$$ This doesn’t ...
Jmh's user avatar
  • 153
12 votes
4 answers
3k views

Integrating acceleration - wrong choice of bounds in textbooks?

I've noticed in my physics textbook (and in a lot of other popular sources), that the process of integrating non-constant acceleration to get to a velocity formula, the integrating bounds imposed on ...
Ius Klesar's user avatar
11 votes
4 answers
3k views

When the direction of a movement changes, is the object at rest at some time?

The question I asked was disputed amongst XVIIe century physicists (at least before the invention of calculus). Reference: Spinoza, Principles of Descartes' philosophy ( Part II: Descartes' Physics, ...
user avatar
11 votes
2 answers
3k views

Kinematic equation as infinite sum

I'm not sure exactly how to phrase this question, but here it goes: $v=\dfrac{dx}{dt}$ therefore $x=x_0+vt$ UNLESS there's an acceleration, in which case $a=\dfrac{dv}{dt}$ therefore $x=x_0+v_0t+\...
gen-ℤ ready to perish's user avatar
9 votes
4 answers
2k views

Can I find the acceleration or velocity when my displacement-time graph is discontinuous?

Today, I encountered the problem where I was asked to find the velocity and acceleration from displacement-time graph but the displacement-time graph was discontinuous. So I am unable to find the ...
Roger Michealson's user avatar
7 votes
6 answers
2k views

Can acceleration depend linearly on velocity?

Is it possible that acceleration may vary linearly with velocity. Is it practically possible, if so is there a practical example of it? By integration I was able to verify that for the above case to ...
Gurjot Singh's user avatar
6 votes
6 answers
1k views

Question about derivation of kinematics equations

Apologies if this has been asked before, but I browsed the sub and couldn't find something specific. I understand the derivation for one of the equations as follows: \begin{gather} \frac{dv}{dt} = a ...
ChemSniper's user avatar
5 votes
2 answers
2k views

How does instantaneous velocity or acceleration have any other numerical value than 0? [duplicate]

Instantaneous velocity is defined as the limit of average velocity as the time interval ∆t becomes infinitesimally small. Average velocity is defined as the change in position divided by the time ...
McFluff's user avatar
  • 153
5 votes
2 answers
2k views

Why does acceleration need to be constant if integrating?

My teacher wrote the following: Constant Acceleration If acceleration is constant, then: $$\vec{v}(t) = \int_0^t \vec{a}(t')dt'\ + \vec{v_0}$$ and $$\vec{x}(t) = \int_0^t \vec{v}(t')dt'\ + \vec{...
rb612's user avatar
  • 1,177
4 votes
2 answers
2k views

Calculating Intensity/Strength of Vibration with 3DOF

I want to calculate the intensity/strength of vibration at a given location. I have measured the acceleration at this location, using an accelerometer. So my measures look for example like: ...
Robin's user avatar
  • 43
3 votes
4 answers
2k views

If displacement is 0, does that mean initial velocity equals final velocity?

For instance, one of the kinematic equations is : $$v_f^2 = v_i^2 + 2ad$$ where $v_f$ is final velocity, $v_i$ is initial velocity, $a$ is acceleration, and $d$ is displacement. Say for instance a guy ...
Pro Grammar's user avatar
3 votes
3 answers
357 views

Calculating displacement from acceleration (intuitively) [closed]

If I say acceleration of car is constant at $4\; \rm m/s^2$. Then isn’t it that it covers $4\; \rm m$ in $1\; \rm s$ with velocity $4\; \rm m/s$. Then in $2\; \rm s$, the velocity is $8\; \rm m/s$. ...
Srijan's user avatar
  • 725
3 votes
2 answers
285 views

Motion with constant speed and constant acceleration magnitude

I was reading this and this posts. From what I gather In 2D: Constant speed $||\dot x||=const$ and constant positive magnitude of the acceleration $||\ddot x|| = const$ imply circular motion. In 3D: ...
Euler_Salter's user avatar

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