All Questions
103 questions
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votes
1
answer
58
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Need help in understanding Tangential Acceleration [closed]
I am studying Circular motion and I am confused about tangential acceleration and tangential velocity. I am studying uniform circular motion and it says the tangential acceleration is $0$ in uniform ...
-1
votes
1
answer
44
views
Components of velocity in projectile motion [closed]
I came across this question in my physics textbook (Gr12) and I was hoping someone could explain the solution to me
A ball is thrown horizontally off a building at $8.2\,\text{m}/\text{s}$. At a ...
- 3
0
votes
2
answers
49
views
Equations of motion for constant acceleration
I read that the equations of motion for a constant acceleration can be represented in a scalar form as well as a vector form, but what's the need to do them in vector form what extra can we do by ...
- 51
-1
votes
1
answer
49
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Finding radial acceleration from $xy$ vector cordinate [closed]
I know that is a silly question but i cant figure it out.
Suppose we have
$$ \textbf{R} = A i + B j $$
and want to find the radial acceleration.
We know that the radial acceleration is
$$ \ddot{r} -...
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-2
votes
3
answers
96
views
Why is it wrong to find centripetal acceleration using change of velocity over change of time?
This question asks to find the centripetal acceleration by giving the initial and final velocity over the change of time.
As shown, my book combined two rules to find the acceleration. I utterly ...
- 377
-2
votes
1
answer
91
views
From where does the expression of the tangential accerelation come from?
I've seen so many times that the expression of the tangential acceleration is known to be: $$a_t=\ddot{s}$$ but from the expression of the acceleration in spherical coordinates, in the tangential ...
- 69
4
votes
2
answers
623
views
Is there a relationship between the magnitude of the velocity and acceleration vector?
Given a path, how do the magnitude of the velocity and acceleration vector along the path correlate? I am confused due to the fact that the acceleration is the change of velocity over time and in ...
- 41
2
votes
1
answer
72
views
(Circular motion) Acceleration is given, so why asked for more? [closed]
The full question is below.
A car starts from rest and moves around a circular track of radius $32.0\,\text m$. Its speed increases at the constant rate of $0.500\,\text{m/s}^2$.
(a) What is the ...
- 21
0
votes
2
answers
414
views
Why does tangential acceleration become 0 when the velocity is max? [closed]
I know that tangential acceleration equal to zero when the circular motion is uniform, but why is it equal to zero, when the velocity is max or min? Because there is no relation between the value of ...
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0
votes
1
answer
43
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Are terms tangential acceleration and normal acceleration only used for instantaneous velocity?
Are terms tangential acceleration and normal acceleration only used
for instantaneous velocity?
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1
vote
6
answers
113
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If a body moves along a path (any path, not just circular) with constant speed, is it's tangential acceleration necessarily zero?
If a body moves along a path (any path, not just circular) with constant speed, is it's tangential acceleration necessarily zero?
I could only find general proofs for the case of circular motion and ...
6
votes
4
answers
838
views
How can I write the vector form of this equation, $a = vdv/dx$?
My Physics teacher was deriving the 'Work-Energy Theorem' for a single particle in the class; where after doing the vector addition of all the forces acting on the particle, he put the resultant of ...
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2
votes
4
answers
910
views
Mathematical proof for: Acceleration always orthogonal to its velocity changes its direction
Whenever I ask this doubt that how can force perpendicular to objects velocity can change its direction but cant change its magnitude I get proof for only the magnitude will be constant that is: no ...
- 375
0
votes
2
answers
358
views
Circular motion equivalent in three dimensions [closed]
Are there equations or even a concept of circular motion/tangential acceleration/centripetal acceleration in three dimensions? Maybe something called "spherical acceleration"? or am I just ...
- 75
0
votes
3
answers
244
views
Why does Taylor take the derivative or only $r \bf{\hat r}$ for the velocity/derivative of the position vector?
Why does Taylor take the derivative or only $r \bf{\hat r}$ for the velocity/derivative of the position vector? If the position of an object in Polar coordinates is given by (r, theta), why is the '...
- 312
0
votes
2
answers
229
views
Scalar term for acceleration [duplicate]
Consider the following definitions:
Distance is the magnitude of the displacement
Speed is the magnitude of the velocity
X is the magnitude of the acceleration
Is ...
- 115
0
votes
1
answer
213
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Is there anything like negative deceleration?
I kinda understand acceleration, deceleration and negative acceleration but does anything like negative deceleration exist?
- 137
-3
votes
2
answers
267
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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 ...
- 137
0
votes
0
answers
55
views
What do you call $ \frac{d^2 r}{dt^2}$ in polar coordinates? [duplicate]
In polar coordinates, one finds centripetal acceleration as:
$$ a_c = \frac{d^2 r}{dt^2}- \frac{v^2}{r}$$
Where $|r|$ is distance from center to particle, $v$ is tangential velocity.
My question is ...
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15
votes
3
answers
4k
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Why does solving the differential equation for circular motion lead to an illogical result?
In uniform circular motion, acceleration is expressed by the equation
$$a = \frac{v^2}{r}. $$
But this is a differential equation and solving it gets the result $$v = -\frac{r}{c+t}.$$
This doesn’t ...
- 153
0
votes
2
answers
353
views
Why isn't tangential acceleration just always 0?
This is probably a very stupid question but I can't help me.
Tangential acceleration is $\vec{a_t}=\frac{dv}{dt}\frac{\vec{v}}{v}=\frac{\vec{v} \cdot \vec{a}}{v} \frac{\vec{v}}{v}$. Since $\vec{a}$ is ...
- 15
0
votes
1
answer
457
views
Calculating 2D acceleration vector direction to most quickly reach a point
I am currently writing a game where you fly a starship in 2D space. In a given timestep, the ship has the ability to accelerate at constant rate in any direction. The player can specify a point at ...
3
votes
3
answers
727
views
Proof of $a = v^2/r$ using similar triangles
The book states that the ‘change in velocity’ triangle and the displacement triangle has the same angle theta.
But I don’t get it? How can we prove that the two triangles will have the same angle?
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1
vote
2
answers
159
views
One object moves along the cycloid at a constant rate, how about its acceleration? [closed]
We know that the parametric equation:
$$x=R(\theta+\sin(\theta))$$
$$y=-R(1+\cos(\theta))$$
and the constant velocity $c$.
How do I prove that the acceleration of the object in the $y$ direction is ...
- 21
0
votes
0
answers
72
views
Acceleration in polar coordinates
Is transverse acceleration always perpendicular to the normal acceleration, in polar coordinates?
1
vote
2
answers
788
views
How do I get the total acceleration from 3 axes, in negative?
For a project, I'm working with acceleration data recorded by triaxial accelerometers. This means that I have accelerations in the x, y, and z axes. I found the almost exact same question from a few ...
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0
votes
1
answer
109
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For an airplane moving north from some latitude (say $30^{\circ}N$), why does rotation of the Earth cause an increase in apparent drag?
I'm not able to understand the answer to this example:
Example 10 from the Curtis Orbital Mechanics text book :
An airplane of mass $70 000\ \mathrm{ kg}$ is traveling due north at latitude $30^\circ$...
1
vote
2
answers
115
views
Why isn't tangential acceleration just $a$?
If the tangential acceleration is $\mathrm d|v|/\mathrm dt$ then isn't it just the magnitude of the acceleration of the object because $\mathrm dv/\mathrm dt$ is acceleration?
- 139
0
votes
1
answer
129
views
Why intuitively is the tangent vector the derivative of velocity of position with respect to their modulus?
When trying to find the tangential velocity, many textbooks define the tangent direction as one of the following:
or
Intuitively, why is the tangent vector the derivative of the position with ...
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2
votes
7
answers
4k
views
The direction of the velocity of a body can change when its acceleration is constant. How is it possible since acceleration is a vector quantity?
As we already know that acceleration is a vector quantity which means that it has both direction as well as magnitude. It can also change given any one of the two or both (magnitude and direction) ...
9
votes
3
answers
2k
views
Is centripetal acceleration almost perpendicular to velocity or it is exactly perpendicular to velocity?
In all the derivations of centripetal acceleration that I have seen so far, the direction of acceleration is said to be perpendicular to velocity but I think it's not exactly perpendicular to velocity ...
- 463
0
votes
1
answer
146
views
Do accelerations add the same way velocities add in non-relativistic mechanics? [closed]
Can you add and subtract constant accelerations?
user310302
3
votes
2
answers
312
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: ...
- 247
0
votes
1
answer
114
views
Average velocity and acceleration
I know to obtain the average of some vectors I compute the mean of the one dimensional components of each vector and constitute the average vector. My question is : why is this untrue for average ...
- 485
1
vote
5
answers
227
views
Acceleration vector at an extremum
A skier moves along a ski-jump ramp. The ramp is straight from point A to point C and curved from point C onward. The skier speeds up as she moves downhill from point A to point E, where her speed is ...
- 169
0
votes
1
answer
531
views
Proving that acceleration perpendicular to velocity only changes it's direction [duplicate]
In a recent class, I learned about centripetal acceleration and that if a body moves in uniform circular motion the direction of velocity continuously changes implying presence of an acceleration. My ...
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3
votes
2
answers
105
views
Which is the centripetal term here?
In spherical coordinates the acceleration can be written as
$$\textbf{a} = \dot{\textbf{v}} = \ddot{r} \hat{\textbf{r}} + \dot{r} ( \dot{θ} \boldsymbol{\hat{\theta}} + \sin θ \dot{\phi} \boldsymbol{\...
- 1,340
0
votes
1
answer
421
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Equation for four-acceleration
Wikipedia states that
$$ \begin{align} \mathbf{A} =\frac{d\mathbf{U}}{d\tau}
&= \left(\gamma_u\dot\gamma_u c,\gamma_u^2\mathbf a+\gamma_u\dot\gamma_u\mathbf u\right) \\
&= \left(\gamma_u^4\...
- 196
0
votes
3
answers
471
views
What is correct definition of tangential acceleration?
Is tangential acceleration the rate of change of magnitude of velocity
OR,
Is it simply the rate of change of velocity?
I am asking this because I am sort of confused, because there is no tangential ...
-1
votes
2
answers
380
views
When do you add or subtract vectors? [closed]
so I have a question here:
An airplane travelling initially at 240 m/s[28° s of e], takes 35 s to change its velocity to 220 m/s[28°e of s]. what is the average acceleration over this time interval?
...
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0
votes
1
answer
125
views
Apply acceleration that is always opposite to the velocity
I have 2 functions for the $x$ and $y$ components of the velocity of an object ($z$ should always be $0$ in this case)
$$V_x(t)=v_{xi}+\int_0^ta_x(t')dt'$$
$$V_y(t)=v_{yi}+\int_0^t(-g+a_y(t'))dt'$$
...
0
votes
1
answer
3k
views
How to determine the correct time using quadratic functions if there are multiple "correct" roots exist in a 3D system? [closed]
Time can be calculated from a modified kinematics quadratic formula using the initial velocity, displacement, and acceleration. However, the acceleration vector isn't limited to 1 axis.
When applying ...
- 101
0
votes
0
answers
62
views
Why don't we use vector sign for quantities in 1D motion? [duplicate]
My school textbook says that we don't need to use unit vectors (i ,j,k) to represent the direction of vectors in 1D motion as + and - sign indicate direction. But that is creating a lot of confusion ...
- 21
1
vote
1
answer
976
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How is called the magnitude of acceleration? [duplicate]
According to wikipedia page of velocity:
The scalar absolute value (magnitude) of velocity is called speed
and according to wikipedia page of acceleration:
Accelerations are vector quantities (in ...
- 113
0
votes
2
answers
94
views
Using centripetal acceleration to find back the velocity magnitude at $t+dt$
Considering a circular motion with no angular acceleration. How can you find the same magnitude for the velocity vector at different time using the formula $v_{t} = v_0 + a.t$ with vectors?
The ...
- 51
5
votes
2
answers
476
views
Alternative expression of acceleration in vector form
Let's imagine a one dimensional case, where a particle is moving with a velocity $v$ and an acceleration $a$. Thus
$$a=\frac{\mathrm dv}{\mathrm dt}\tag{1}$$
Applying the chain rule, equation $(1)$ ...
user258881
0
votes
2
answers
3k
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Why is there no tangential acceleration in uniform circular motion? [duplicate]
I need to know what all is remains constant in uniform circular motion. The tangential SPEED, angular velocity and centripetal acceleration right? Why is there no tangential acceleration in uniform ...
- 87
0
votes
1
answer
287
views
Trying to prove that the expression for the radial component of the acceleration is equal to $\mathbf v\cdot \mathbf v/r$
I am trying to prove that the normal component of acceleration of a particle undergoing a curvilinear motion is equal to
$\mathbf v\cdot \mathbf v/r$.
Here $\mathbf v$ is the velocity of the particle ...
- 529
2
votes
4
answers
2k
views
Direction of average acceleration in circular motion
I know that the instantaneous acceleration is always directed towards the center of the circle.But what about average acceleration.
In the above figure my book says place change in velocity along the ...
1
vote
2
answers
2k
views
How to convert acceleration projection to angle?
See a simple webpage here, for an object, if one know the acceleration in three direction $\hat x, \hat y,\hat z$, one could extracted two of the angle of the object between the plane that's normal ...
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