All Questions
Tagged with motion or kinematics
4,321 questions
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How does negative velocity and positive acceleration exactly and vice versa slow down objects?
I am confused. How does negative velocity and positive acceleration and vice versa slow down objects? Here are my thoughts. Please let me know if I am correct.
According to Newton's first law of ...
- 12.9k
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38
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Force-simulation for graph layout: How to avoid particle collapsing into a single point?
In a force-based graph-layout simulation using Barnes-Hut, what are the conditions for collapse? With collapse I mean multiple (or even all) nodes "collapsing" into a single point.
Is there ...
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1
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42
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How to decide for correct value of phase difference?
A sinusoidal wave is propagating along a stretched string that lies along x-axis. The wave is moving in +x-direction. Figure shows the graph of transverse displacement of particles of the string at x =...
- 99.9k
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14
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Why do rain drops fall with a constant velocity?
While reading my physics book. I came across a line that says that:
Rain drop falls with a constant velocity because the weight(which is the force of gravity acting on body) of the drop is balanced ...
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1
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113
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Can distance traveled by a body be zero?
I had seen a teacher saying on YouTube that we must note that distance traveled can not be zero then I searched for the same on net and surely some sources say same e.g. the below link
https://byjus....
- 71
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4
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Projectile Motion Components of Velocity and Speed
In kinematics, I am told that the vertical velocity at the apex of projectile motion is 0. There is still a constant horizontal velocity. Given this, are we not allowed to generalize and say that at ...
- 14.9k
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1
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658
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Tangential velocity - Spherical coordinates
In a spherical coordinates system ($r$, $\theta$, $\phi$ ), assuming an angular rotation $\omega_z$ around the z-axis, the tangential velocity of a point can be expressed as:
$$V_x = -\omega_z R \sin\...
CommunityBot
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80
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How does relative motion work for an extended object?
I have this conceptual doubt which might be flawed very badly but I don't understand this particular thing. For example, if one end of a stick is moving with velocity $v_1$ and the other with $v_2$, ...
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1
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45
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Shaking pencil's hyperbola formula? [closed]
When you typically shake a pencil, it bends and forms a curve (hyperbola?). I want to formalize this phenomenon, but I'm not sure how to do it. I'd like to incorporate factors such as amplitude, ...
- 33.4k
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2
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80
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Vectors in inertial and non-inertial frames
Trying to understand how vectors change in inertial and non-inertial frames
Am I right in saying vectors are defined by their invariance under coordinate transformations? My main question is are ...
- 12.9k
2
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2
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816
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Is there a different way to measure speed, other than with time?
A second on Earth is different from a second on the Sun and a second next to a black hole. Therefore speed, as measured in meters per second, is different in each of these locations. Is there an ...
- 213k
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3
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473
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Confusion with Terminal Velocity
So I know that terminal velocity occurs when velocity becomes constant and the body is no longer accelerating.
However using our normal kinematics equation say a body in terminal velocity, the time ...
- 12.9k
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2
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211
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Question on relative velocity [closed]
If a man is moving on a horizontal belt (with constant velocity w.r.t belt)which is also moving in the same direction with some velocity , then time w.r.t belt and w.r.t ground to travel some ...
- 12.9k
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2
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31
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Relative trajectories of two projectile [closed]
Two balls are launched with different initial velocities and at non-coplanar angles (meaning they could be in entirely different planes).Not Considering the effects of air resistance, describe the ...
CommunityBot
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High school kinematics problem [closed]
From a town, cars start at regular intervals of 30 seconds and run towards, another town with a constant speed of 60km/h. At some point of time, all the cars simultaneously have to reduce their speeds ...
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5
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The required energy to accelerate a particle from one velocity to another
Say I have a charged molecule running along a linear evacuated tube (so no wind resistance). In the laboratory frame, we can measure that the particle is moving at some speed $v_1$. Provided that ...
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How to Measure the depth of a Hole by Dropping a Rock? [closed]
Let's say I have a rock and a stopwatch.
I am standing on the edge of a deep hole or canyon, and can see the bottom.
How would I go about measuring the depth of the hole?
- 1,793
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Closed form solution for the linear acceleration of a particle on 3D rotating object given momentum and MoI?
Is there a closed-form solution for the linear acceleration of a particle on a rigid body undergoing some arbitrary rotation in 3D with no external forces, given its angular momentum vector and its ...
- 357
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27
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How to mathematically model a lumped-mass cable model?
I am trying to simulate a 2D cable as a lumped-mass model. I think that it's like a chain of pendulums and I would preferably like to be damped. Just to make sure, this is the cable model that I'm ...
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1
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152
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Lorentz-invariant phase space integral
Consider the following Lorentz invariant integral associated to a $2\to 2$ scattering:
\begin{equation*}
I = \int \frac{d^3\mathbf{p_3}}{(2\pi)^3 2E_3} \int \frac{d^3\mathbf{p_4}}{(2\pi)^3 2E_4} \...
- 213k
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1
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Why don't they use golf ball dimples on bullets or cannon balls? [duplicate]
Dimples help the golf ball to fly far. But do you know why they don't use them on bullets or cannon balls?
Some kinds of cannon ball have similar size as a golf ball.
- 45.7k
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1
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I cannot understand the way these questions were solved [closed]
I was going through the mcqs of my physics book and i stumbled upon this pair of questions.
Source of images: vaia.com
1.Figure gives a snapshot of a wave traveling in the direction of positive xalong ...
- 363k
2
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5
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Find the max projection angle so that distance from point of projection always increases
We want to launch a projectile from the surface of earth so that its distance from the point of projection is always increasing. What is the maximum angle of projection for which this is possible?
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Is it possible to have a uniform speed but variable velocity in one-dimension motion?
Is it possible to have a uniform speed but variable velocity in one-dimension motion? I saw a lecture where teacher said that it is possible if particle changes its direction of motion 180$^\circ$.
...
- 41k
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1
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Does drag coefficient vary with size?
Take three spheres having respectively a 1 meter, 100 meters and 1000 meters diameter. Size aside they don’t differ in any other way.
They’re moving through a fluid at the same, constant velocity of 3 ...
- 12.9k
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1
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47
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A change in the unit vector over a finite time interval
how we can write the change in unit vectors over a finite time interval, the change in unit vectors in an infinitesimally small-time interval 'dt' is given by the magnitude of the really small angle ...
- 23.3k
13
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4
answers
1k
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How do we measure the position of a body? [duplicate]
I am a high school student and I was studying kinematics about position of a body. So, one thing I do not understand in this diagram is the position of woman. Initally, at $t=0$, this woman was at $...
- 52.3k
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4
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213
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Why acceleration is not always parallel to velocity but velocity is always parallel to displacement? [closed]
Velocity is derivative of displacement :
$$\vec v=\frac{\mathrm {d\vec r}}{\mathrm dt}$$
And acceleration is derivative of velocity.
$$\vec a=\frac{\mathrm {d\vec v}}{\mathrm dt}$$
Given that their ...
- 213k
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3
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Are the concepts of motion such as mass, momentum, impulse, work, energy, force etc. fictitious/abstract concepts or are they real "things"?
I am a first-year undergrad studying maths and physics and whenever my professor introduces these concepts and the derivations of their associated laws i.e. conservation of momentum, work-energy ...
- 51.7k
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141
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What is the point/meaning of a trajectory equation
I have just learned about the trajectory equation and it is defined as such in my textbook
An equation that relates the position vector of displacement(but not distance) of a particle along x and y ...
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5
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6k
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Are all objects in motion?
It seems like everything in the universe is in motion, at least relative to some other object. That leads me to believe that all objects are in motion. But how do we measure motion when we are ...
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2
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308
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What is the physical significance of momentum and energy in kinematics?
Thank you all for the insightful comments on my previous question Are the concepts of motion such as mass, momentum, impulse, work, energy, force etc. fictitious/abstract concepts or are they real &...
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3
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Why is it suitable to use $s= \frac{1}{2}at^2$ in this situation?
Question: A car slows down uniformly on a straight road, and come to rest in 3 m . What is the ratio of the time it takes to travel each of these three metres?
So this may be quite a simple question ...
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Threshold energy formula
In Krane's Introductory Nuclear Physics, in chapter 11, he uses the conservation of energy and momentum to derive the formula for the threshold energy of a reaction a + X → b + Y (with X being an ...
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1
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47
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The locus of the velocity vectors of a boat navigating in the sea under the presence of a very strong wind?
I already asked a question very similar to this one here and I think the solution would not work when the boat navigates in the sea when a very strong wind blows. That is I am trying to find the ...
- 213k
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What is the locus of the velocity vectors of a boat navigating in the sea under the presence of some force?
I am a mathematician and know nothing about physics, although I am trying to solve a problem related to physics. If someone could help or provide some suggestions, I would be grateful.
I have a speedy ...
- 12.9k
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1
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49
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Shapes of waves in the surface of a pond when the breeze blows
When I throw a stone into a pond while a breeze is blowing across its surface and the water is at rest, what would be the shapes of the waves?
Before the wind, the shape of the waves is circular. Then ...
- 3,321
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2
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How to calculate the final position of a particle under variable accelaration and its instantenous velocity?
I'm a first-semester physics student who was recently on a train. On a screen, it said the instantaneous velocity of the train was 176 km / h. We had 4 min left until our destination. I wanted to ...
- 39.3k
2
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1
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Doubt regarding Velocity-Time graph with Constant Accleration [closed]
I think the answer is (A) initially. However, what about option (C)? It also shows a graph with constant acceleration and a negative slope. And in option (E), the acceleration is 0. Can we consider ...
- 213k
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2
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84
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Solving a PDE using $x-vt$ as a variable
So I was reading this Landau and Lifshitz paper:
https://doi.org/10.1016/B978-0-08-036364-6.50008-9
The article can also be found without a paywall by just searching its title, "On the Theory of ...
- 45.7k
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2
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What is closing speed?
what is closing speed? the only information google was able to give me, is that closing speed is when a car is approaching another car both at 30m/s the closing speed is 60m/s, so what exactly is ...
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What is the equation if that projection starts SHM on the $x$-axis from extreme position?
Consider A particle performing Uniform Circular Motion.
We know that its projection on diameter performs SHM.
Then, if that projection starts SHM on the y axis from mean position, then $y=A\text{sin}(...
- 41k
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In $a = dv/dt$, is $a$ the net acceleration? [closed]
While going through the calculus approach to accelerate, we have,
$$a = dv/dt, $$
I think, here, v and a should be in the same axis,
is my process correct?
in a planar motion in two dimensions, it ...
- 4,609
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2
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95
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Where do exerted forces come from?
I think my confusion stems from this: if a book is resting on a table I understand that the force of gravity acts on the book and as it is in equilibrium, the table exerts a force equal in magnitude ...
- 77.9k
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1
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Derivation of the function for the position of a particle given that a constant force acts on the particle which always points to fixed point [closed]
A particle of mass $m$ is moving with initial velocity v. A constant force F acts on the particle in a direction which always points to a fixed point P. If initially the direction of v was ...
- 213k
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0
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Simulating two-body decays in the specific direction
How to simulate the 2-body decay of some particle with mass $m$ moving with the given 4-momentum $p^{\mu}$ into two particles 1,2 with masses $m_{1}, m_{2}$ such that, say, the particle 1 will have ...
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When a bus goes around a corner, does the person sitting at the back travel further distance than the person sitting at the front?
This is a bit of childish question.
When a bus goes around a corner, does the person sitting at the back travel further distance than the person sitting at the front?
My thought is no because the bus ...
- 12.9k
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1
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55
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How to explain the phenomenon of air bag, when have one object hit air bag and one object catapult from air bag
Problem of this phenomenon is in title.To describe this, I separate it into 3 phases;
M1 hit airbag, 2) Air moving inside air bag caused by pressure gradient ,
3)M2 flew away caused by air moving to ...
- 28k
5
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3
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Where does the negative sign disappear?
The defining equation for simple harmonic motion is such
$$a=-ω^2x$$
When we find the centripetal acceleration of an object in orbit we use the formula
$$a=ω^2r$$
As a consequence of the accleration ...
- 12.9k
1
vote
2
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142
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Average velocity showing different results
I was solving a question, in which, a particle has travelled a distance $s$, with initial velocity $0$ and constant acceleration.
So the equation of motion becomes,
$$ v = a t \tag{1} $$
and
$$ v = \...
- 28.8k