The time rate of change of the position of an object

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3
votes
2answers
152 views

How are the theoretical properties of a gravity train linked to orbital properties?

Whilst perusing a question on WorldBuilding, a link was given to an article about Gravity Trains. Some of the answers on the question, and the Wikipedia article, state a travel time of 42 minutes ...
4
votes
3answers
6k views

What is displacement? Position relative to a reference point or change of position

What is the "official" or most useful definition of displacement in the context of kinematics? There are two common ones: Displacement is the length and direction of a line from a fixed reference ...
2
votes
3answers
557 views

What is the relationship between rolling resistance and velocity?

I'm a games programmer, trying to write a simple car physics simulation. I'm aware that a car travelling in a straight line will exert a traction force that drives it forwards (by turning the wheels ...
-6
votes
1answer
51 views

Can velocity be negative? [closed]

In free fall I use the formula V=g*t and g is negative(-9.8m/s^2). It gives me negative.
1
vote
1answer
30 views

Systematic+Random Uncertainty for velocity measurement

I have a question regarding systematic and random uncertainties. I have to measure the mean value of a velocity measurement in flow field at a point. I've recorded say 1000 samples in time, which I ...
0
votes
2answers
54 views

Application of Bernoulli's equation to siphon

I'm trying to understand how to use Bernoulli's equation in practice. So I will make an example of where is my confusion. I found this great explanation on Wikipedia about the siphon, but there is a ...
13
votes
3answers
4k views

How to derive addition of velocities without the Lorentz transformation?

Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities $$w~=~\dfrac{u+v}{1+uv/c^2}$$ without Lorentz ...
1
vote
0answers
28 views
0
votes
1answer
57 views

If two cars have the same acceleration at time $t$, are the velocities of the cars the same at time $t$?

So when I look at the question logically, I reason that if I had two cars: Range Rover and BMW, at time t, I could pump the gas and make them accelerate at the same rate at 0.5 m/s^2 but I could be ...
1
vote
0answers
85 views

The path that a light beam takes in empty space

First excuse me if this question is very simple for you but for me and for my friend is not. Recently we were discussing what path a light beam will follow in a box moving at a constant velocity in ...
2
votes
0answers
20 views

Velocity Profile of the Upper Atmosphere

Consider an Earth-Centered Inertial (ECI) frame in which the tangential (to Earth's surface) velocity is measured. Now consider obtaining constant average velocity profiles of the atmosphere as a ...
1
vote
1answer
39 views

Calculating relative velocity in three dimensional space

Given two points $\mathcal{A}$ and $\mathcal{B}$ in $\mathbb{R^3}$ whose position and velocity vectors are, respectively: $$\mathbf{r_A}=\begin{pmatrix}r_{A_{x}}\\r_{A_{y}}\\r_{A_{z}}\end{pmatrix}$$ $$...
-2
votes
1answer
146 views

How to find initial direction of an object using components [closed]

I have a basic (not for me) physics question that I am struggling to get my head around. It involves a car moving at an unknown speed that explodes into 3 pieces. I am having trouble finding the ...
-1
votes
5answers
106 views

How can I find initial and final velocity? [closed]

Is there a way to find initial and final velocity if I only know the acceleration and distance and which formula must I use? I do not know the time either. EDIT Thank you for all your answers! You ...
-1
votes
1answer
49 views

Time traveled assuming instant acceleration/decelaration

I am working on sort of a motion planning algorithm where I need to estimate the time it takes to travel along a certain path of points (straight lines between consecutive points, i.e I am assuming ...
1
vote
2answers
35 views

Velocity over time applying constant power and considering air drag

I wanted to understand how velocity changes over time when applying a constant power to a body of mass $m$. I figured out that in this case, since $$P=d/dt(KE)=d/dt(\frac{1}{2}mv^2),$$ integrating I ...
3
votes
2answers
76 views

Throwing masses to gain velocity. A question of efficiency

I was thinking the other day of a system in which you eject mass. And then I wonder whether it was more efficient to throw a big mass or many little. Let me put it in other terms. Suppose you are ...
0
votes
1answer
16 views

Trasversal wave on a rod velocity

What is the velocity of a trasversal wave on a metal rod? Does it depend on the shear modulus $G$ $$v_{t}=\sqrt{\frac{G}{\rho}}$$ Or on the tension $T$ of the rod? $$v_{t}=\sqrt{\frac{T}{\rho}}$...
0
votes
2answers
31 views

Velocity of the points of a rigid body

The most general motion of a rigid body is a roto-traslation. Firstly is it correct that any point (let's call it $O$) of the rigid body can be seen as the point through which passes a istantaneous ...
0
votes
1answer
41 views

Calculating the Velocity of an object far far away

I saw a satellite the other day, it moved very fast through the night sky. Now I know it took around 110 seconds for it to fully travel out of the night sky(out of my visual bounds assuming, that I'...
0
votes
0answers
20 views

Water Jet scenario [duplicate]

So I have a question I came across that goes along the lines of Water is discharged from a 20 mm diameter nozzle to the atmosphere. The water jet leaves the nozzle with a velocity of 12 m/s and is ...
-1
votes
3answers
58 views

How to show that distance travelled in the $n$'th time interval grows in arithmetic progression [closed]

$\mathbf Q.$ A car starting from rest and accelerating uniformly travels a distance $d$ in the first $n$ seconds and a distance $k$ in the next $n$ seconds. Prove that $ k=3d$ Attempt: $$d=(v_1)(n)$$...
-2
votes
1answer
78 views

What does $P = Fv$ mean? [closed]

The engine of a car is developing a power of 90kW when it is moving on a horizontal road at a constant speed of 100 km h−1. Estimate the total horizontal force opposing the motion of the car. I ...
0
votes
1answer
53 views

How do they know their velocity in a spaceship? [closed]

Suppose a spaceship is going to Mars or to Jupiter, they switch on their thrusters and accelerate for a certain period, how to they know their position / velocity, do they refer to the Sun?
0
votes
0answers
41 views

Relating Initial velocity and acceleration to distance traveled up a ramp

This is the situation: I am conducting research on the ability of fin-fish to scale short wetted ramps for use alongside sea-lamprey barriers to allow non-target species to pass these barriers. We ...
5
votes
3answers
181 views

Velocity in a turning reference frame

I often see the relation that $\vec v=\vec v_0+ \vec \omega \times \vec r$ in a turning reference frame, but where does it actually come from and how do I arrive at the acceleration being $$\vec a=\...
0
votes
2answers
152 views

How to calculate acceleration from discrete samples of velocity?

I have a device that I made which is able to calculate distance moved and can determine time. I take samples of time every x distance. Giving me n velocity samples. I currently show the user 2 ...
-1
votes
3answers
87 views

Velocity of water from a certain depth

I was curious to know does water come out of a certain depth when there is a difference in pressure, and also if it does come out of a certain depth, at what velocity does it travel at? So, ...
0
votes
2answers
67 views

velocity of water exiting a 20 m hole at the bottom of water column 5000 m in height

What would be the velocity of water exiting a tube that has a height of 5000 m from a hole with a diameter of 20 m at the bottom, if the height of the water remains constant at 5000 m? Would it be ...
5
votes
1answer
382 views

Does tunneling transmission probability depend on the density of states or velocity?

In some quantum text books [1], the tunneling transmission formula depends only on the density of states of 2 regions (DOS) involved in tunneling. ($T(E) = C \times DOS_1(E) \times DOS_2(E)$, where C ...
5
votes
2answers
834 views

What is the terminal velocity of a sheep?

Inspired by this question on Gaming.SE Using actual in-real-life physics, what would the terminal velocity of a sheep actually be? I would assume it would be around 50m/s, but I might be wrong. ...
0
votes
2answers
35 views

In Golf, What Influences More On How Far The Ball Travels?

Most of us are aware of the general concept that the harder you hit something, the farther it usually travels. (let us suppose we are neglecting any air resistance and friction that happens) And from ...
1
vote
1answer
31 views

Phase difference in SHM between spatial coordinate and velocity

In simple harmonic motion the spatial coordinate $x(t)$ and the velocity $v(t)$ have a phase difference of $\frac{\pi}{2}$ and I'm totally ok with that. But I also saw that the difference in the phase ...
1
vote
0answers
57 views

Determining the forces required to maintain a static center of mass position; one with velocity and one with acceleration [closed]

I'm having a bit of trouble wrapping my head around this conceptually. The magnitudes and directions of the forces on two of the particles are indicated. What are the magnitude and direction of the ...
0
votes
0answers
13 views

Velocity in harmonic motion - Why are these angles congruent?

I learned about harmonic motion and I found the derivation of the formulas: And so, the velocity in harmonic motion is the projection of the velocity in angular motion. The only thing that is not ...
1
vote
1answer
37 views

Can angular momentum not be conserved in a straight line motion?

Consider a particle moving an a straight line, with constant velocity $v$. The angular momentum (pivot point $O$) can be calculated as $$L=mr v_{\theta}$$Where $v_{\theta}$ is the velocity ...
1
vote
0answers
47 views

Bernoulli principle and falling object

Consider the following situation, also depicted in the picture bellow (and please excuse my lack of Paint skills): A helicopter is flying at a constante altitude, and hovering the same ground spot. ...
0
votes
3answers
8k views

Work, Energy & Power - Body slides down a hemisphere

A small body of mass $m$ slides down from the top of a hemisphere of radius $r$. There is no friction between the surface of the block and the hemisphere. The height at which the body loses contact ...
0
votes
0answers
33 views

How to derive velocity, distance from a changing acceleration?

I'm making a electronic device that is out of the scope of this site, but essentially it gives me acceleration readings every X microseconds. Given these samples of acceleration, how can I find out ...
0
votes
1answer
33 views

Multiple Objects at Constant Speed

Imagine 1 million objects travelling in space, at a constant speed, along an imaginary line. They don't deviate from that line for the sake of this argument. Now, object 1 has a velocity of $v_{1}=1$ ...
0
votes
0answers
31 views

For two electron that moving parallel,can we using this equation for Electric Field and Magnetic Field?

i suppose we have two electron and they are moving parallel,please see picture: my question is can we use this this equation for it? Griffiths' Introduction to electrodynamics): $$\vec E(\vec r,t)=\...
-1
votes
2answers
29 views

Proof regarding angle between velocity vectors

Consider a casual trajectory of a point and the velocity vector at two istants $v_1$ and $v_2$. In picture (1) I considered the osculating circle with center $O$ and radius $R$. In the picture (2) I ...
-3
votes
1answer
41 views

How do you know when to use kinematic equations as apposed to $v = d/t$ and $a = v/t$? [closed]

How do I know when to use v = d/t and a = v/t or d=vi+​1/2​​at^2 and vf = vi + at?​
0
votes
2answers
69 views

How to determine the net velocity change applied by a force vector [closed]

I am a little stumped by the answer of this question. The question reads, "In three situations, a single force acts on a moving particle. Here are the velocities (at that instant) and the forces: ...
0
votes
2answers
383 views

How to achieve speeds faster than light? [duplicate]

So, I heard that all speed is relative. And that nothing can travel faster than light. Then I guess it is OK for a spaceship to leave Earth at 0.6c constant speed. And what if an other spaceship were ...
47
votes
6answers
6k views

If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?

Let's say I fire a bus through space at (almost) the speed of light in vacuum. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus toward the front, does that mean I'm ...
0
votes
2answers
59 views

Position, velocity and acceleration vs time graphs

I'd like to draw graphs of a vehicle and I have a position vs time table. I can set the points but how am I supposed to join them, straight or hyperbole ? If the object is accelerating which is yes ...
1
vote
1answer
122 views

Are velocity and acceleration smooth quantities?

My thinking: acceleration corresponds to a force which is instantaneous, so the acceleration of a rigid body can be rather spiky (non-smooth) velocity (angular velocity) describes the ratio of ...
2
votes
2answers
58 views

Does the position-time graph have to be a smooth function?

If at some time $t$ there were a discontinuity in the velocity-time graph, then the acceleration would be infinite at $t$. So intuitively, it seems that the velocity-time graph must be continuous. I ...