The time rate of change of the position of an object

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4
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3answers
147 views

Do bullet/gun physics change if the gun is traveling very fast?

If I'm running at say $400\: \mathrm{m/s}$ and a bullet travels at $400\: \mathrm{m/s}$ and I fire the gun, will I see the bullet leave the barrel? I either see it stay in the barrel floating ...
0
votes
1answer
558 views

Phonon dispersion calculation based on velocity autocorrelation function in reciprocal space?

I would like to ask about the method of calculating phonon dispersion relation. Up to my knowledge, there are 2 methods to calculate the phonon dispersion: By diagonalizing the dynamics matrix. ...
2
votes
2answers
111 views

Relative velocities of boats and a stone thrown by the boat [closed]

Question: A police boat is chasing a boat with criminals along a straight river by moving against the stream. The speed of the river stream is 3 miles per hour, the speed of the boat with ...
-2
votes
3answers
151 views

Velocity of the photon

As far as I know photon travels in a wave pattern, that means it has $x$ and $y$ axis velocity components. If photon travels along $x$ axis, then what is it's maximum $y$ axis velocity?
1
vote
2answers
10k views

What is the difference between angular speed and tangential speed in a circular motion?

I was looking a long time for the way the equations of this two speeds are obtained, and i found pretty much nothing important, so can someone explain how are those obtained, and which is the ...
0
votes
3answers
145 views

Interpreting the equation $\vec F = R\vec v$

The Aristotle's law of motion, which is incorrect, states that The velocity of an object $\vec v$ is directly proportional to the force $\vec F$ acting on it or $\vec F \propto \vec v$ ...
2
votes
1answer
371 views

Where do the equations for resistive force come from?

I've been watching MIT's Walter Lewin physics lectures. In lecture 12, Lewin pulls, out of nowhere, a couple of equations regarding resistive/drag forces in fluids: $$\begin{align} \vec{F_{res}} ...
8
votes
2answers
266 views

What is the physical meaning of $|f''(\xi )|\leq\frac{4(f(b)-f(a))}{(b-a)^{2}}$ where $f(t)$ is position as a function of time?

Here is the full problem: I was able to prove the given expression; but the interpretation part is giving me a bit of trouble. Here is my interpretation: The average acceleration in $(a,b)$, is ...
1
vote
1answer
136 views

Angular Momentum of Two Non-interacting Particles

I'm reading a book (An Introduction to Mechanics by Kleppner) where they calculate the angular momentum $l$ of a system of two non-interacting particles, but I don't understant what are they doing. ...
1
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0answers
22 views

How far will the first spacecraft travel before the second one catches up to it? [closed]

A spacecraft leaves the point of origin and has a maximum acceleration of 30 m/s. It can only maintain this rate for 10 minutes before it runs out of gas and then proceeds to drift at a constant ...
1
vote
0answers
86 views

How to formally write down the Boltzmann equation?

Can someone write down the Boltzmann equation, not neglecting any of the variables of the involved functions and integrals? Specifically, how to concisely capture the "primed" variables in a sensible ...
2
votes
4answers
628 views

Why do people claim electrons are accelerating

A lot of text books mention that one of the reasons that classical mechanics failed to explain atomic and subatomic processes is that electrons which accelerate should release energy in the form of ...
0
votes
3answers
124 views

I'm having trouble wrapping my head around force, and thus acceleration, diminishing with a higher velocity when using a constant power

Here is an hypothetical situation I thought about that I don't understand. Let's say I have 2 identical rockets with a fixed power. These rockets start to race in the same direction using the full ...
0
votes
1answer
83 views

The physical interpretation of limit of ratio of two functions

Imagine we have two different differentiable functions $f(t)$ and $g(t)$ where $t$ generally represents the time, if there exists the following limit as $$ \lim\limits_{t\rightarrow \infty } \frac{\| ...
4
votes
2answers
1k views

If starting speed is faster than terminal velocity then what?

If an object is say thrown down (vertically) at an initial speed that is faster than its terminal velocity, what would happen to that objects speed? Would it slow down?
1
vote
1answer
117 views

determining orbit parameters (eccentricity, length and angle of major axis)

I'm trying to make an orbit simulator, and I want to draw the orbit of a satellite given its position and velocity vectors in a 2-D plane. I found this other question which tells how to calculate ...
2
votes
1answer
217 views

Isn't the front edge of a wave, kind of “information” which travels faster than light?

Considering the definition of phase and group velocities, We know group velocity can't exceed C but phase velocity can be infinitely high. Assume a monochromatic electromagnetic wave traveling with a ...
0
votes
1answer
247 views

Simple Acceleration Problem throwing me off

I am having trouble with this problem from my homework. I have gone over it many times, and I must have some concept wrong. A rocket is launched from the ground with constant acceleration. After 4 ...
2
votes
0answers
37 views

How do we generalize limitations on the propagation speed of sinusoidal waves to limitations for transmitting any kind of information?

Our calculations on EM waves basically deal with harmonic waves and through such calculations and relations, we derive some relations and limitations for wave like phenomena. Of these relations are ...
0
votes
3answers
386 views

Parachute in vacuum

Consider that the earth is vacuum. Consider a person of weight 100 kg is falling from sky with an parachute . He is free falling at height of 3000 m. When will he reach the ground? What would happen ...
1
vote
1answer
134 views

If the velocity of particle $A$ exceeds that of $B$, is the acceleration of $A$ greater than $B$?

Two particles $A, B$ are travelling along parallel straight paths. At some point, the velocity of $A$ exceeds that of $B$. Does this necessarily mean that the acceleration of $A$ is greater than the ...
3
votes
1answer
511 views

What is the physics behind Roger Federer's & Rafael Nadal's iconic shots

Two Iconic players of Tennis, Roger Federer & Rafael Nadal, with two iconic shots. One with a top spin forehand & other with a slice backhand. I want to understand the physics of these two ...
1
vote
4answers
861 views

When we take time derivative of a function of time, then is the result another function of time, again?

(I'll try to explain my question by one known example), for example where the velocity is a function of time v(t) then its time derivative (which is acceleration: $a=\frac {dv}{dt}$) is another ...
1
vote
4answers
3k views

Deriving equations of motion using integration

Please refer to my school textbook pg48 (of the book, and not the pdf counter) here: http://ncertbooks.prashanthellina.com/class_11.Physics.PhysicsPartI/ch-3.pdf My doubt is in this context: (right ...
2
votes
0answers
162 views

Saturn V specific impulse issue in velocity modelling with Tsiolkovsky's equation against actual values?

I've been trying to model the Saturn V's velocity using Tsiolkovsky's ideal rocket equation, and in the process, I think I may have made a mistake with regards to the specific impulse? I've come up ...
-1
votes
2answers
306 views

Why terminal velocity exists?

Why the acceleration of free-falling bodies become zero after some time? My only idea would be that the closer to the core of Earth we are, the value of "g" the lower becomes (since the mass below the ...
2
votes
2answers
220 views

Understanding units manipulation (speed of falling coconut after 20m)

When I was on holidays, I was told a story about how someone passing under a palmtree and almost got a coconut fall on his head. Given that these palmtrees where about $20m$ high, we wondered at what ...
0
votes
0answers
66 views

Where does the transformation of $\gamma$ come from?

I was reading Tipler, and in his book he says that in order to transform energy, we must write gamma in terms of quantities in the non-primed frame. However his derivation makes no sense to me, it's ...
-1
votes
1answer
138 views

Why is there no such thing as a body in a state of acceleration?

It appears that velocity is a quantity of motion meaning that all objects can have assigned to them a particular velocity. Through the application of forces (ex: gravity, E&m) we measure changes ...
0
votes
3answers
462 views

Velocity is “Distance/Time” in a particular direction OR simply “Displacement/Time”?

Is velocity: Distance/Time in a particular direction, or simply Displacement/Time? Or both 1 and 2 is the same thing?
0
votes
1answer
445 views

Resisting force depends on velocity? [duplicate]

Why does resisting force depend on velocity? I think there is no relation between resisting force and velocity of object. Please speak about it logically.
-4
votes
1answer
2k views

man walking in rain:relative velocity [closed]

A man walking in rain at a speed of 3kmph find rain to be falling vertically. When he increases his speed to 6 kmph, he finds rain meeting him at an angle of 45 deg to the vertical. What is the ...
-9
votes
3answers
187 views

Is there any other mathematical tool to measure velocity, instead useing derivative? [closed]

To measure velocity we use derivative $$v=\frac {dr}{dt}.$$ Is the any other mathematical tool to do this?
0
votes
1answer
769 views

Help finding Delta T for a known position displacement with known accel/decel, etc

I'm looking for an equation to find the time it will take for a position displacement to happen, given known $V_{max}$, a (known) constant acceleration, deceleration, jerk, and displacement... and an ...
3
votes
3answers
2k views

Mass of particle near light speed in a medium

I am trying to get a common understanding from these two previous questions: Why does the mass of an object increase when its speed approaches that of light? What happens if light/particles exceeded ...
0
votes
0answers
66 views

Outflow for fluid simulation based on “Stable Fluids”

I've implemented a fluid simulation based on the paper Stable Fluids. It works quite well, except I would like to have the velocity at the "upper" edge just to outflow and not to re-enter on the ...
1
vote
0answers
60 views

What do the components of light velocity look like in polar coordinates?

The Schwarzschild solution makes use of polar coordinates, and I'm wondering how the different components of velocity of light change with the position. Might I get some examples of light velocity ...
-6
votes
1answer
1k views

How to derive the Time Dilation formula given: [closed]

Since I do not have 10 reputation I will fit this all in one image: If you have any questions please dont hesitate to ask. EDIT: http://img16.imageshack.us/img16/8604/myquestion2.png
1
vote
0answers
59 views

Two impulses on body

Say I have a physics simulation with a single body with three degrees of freedom (two axis and rotation). I have two impulses of equal magnitude in opposite directions. When applying these impulses in ...
3
votes
1answer
90 views

Nonlinear combination of velocities implies no absolute time?

Landau 1961 begins with a brief presentation of special relativity. This question is about the validity of a certain argument that they use in building up the foundations of the subject from scratch, ...
2
votes
2answers
66 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 ...
1
vote
1answer
90 views

Why pulse waves results in wave packets?

I was doing experiments of measuring sonic velocity and I generate pulse waves from sensor 1, but when they are received by sensor 2, I saw wave packets on the oscilloscope, can you explain why? I was ...
1
vote
3answers
330 views

Functions of Time

1) Is position a function of time only or also velocity? Likewise, is velocity a function of time only or also the position? 2) The following are functions of time: $s(t)$ = distance a particle ...
7
votes
2answers
3k views

Explanation that air drag is proportional to speed or square speed?

A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ...
1
vote
1answer
173 views

Do these equations apply to an object on a zip line or slope?

I was looking at the conversion equations for Potential Energy to Kinetic Energy to Velocity here: http://www.ftexploring.com/energy/PE-to-KE.html Would these apply to an object on a zip-line? ...
3
votes
0answers
210 views

Finding the terminal velocity of a magnet dropped in a solenoid

We have to find proportionality of the terminal velocity with the factors of the system: Plot: a small dipole(mass $m$) with dipole moment $\mu$ is dropped in a long solenoid (radius $r$, ...
4
votes
4answers
7k views

Terminal velocity of all falling objects is same?

Ideally 2 objects of different mass and weight will hit the floor at same time because they face same gravitational pull and accelerate. Will the terminal velocity of both objects be same also? and ...
0
votes
1answer
804 views

Difference between velocity vectors, relative speed

Consider two particles moving in the same direction instantaneously but one of them follows a circular path and one follows a straight path. If I adopt a rotating frame of reference in which the ...
0
votes
1answer
1k views

Relative Velocity problem

I was solving many problems on relative velocity and observed that when the question asks, "what is the minimum time taken by the boat/man to cross the river.?" so the solution says that he ...
-2
votes
1answer
196 views

How to smooth a path (and speed calculation) based on randomly timed coordinates? [closed]

first my actual problem. then my try on improving the current way of solving this with the wish for feedback or even a solution :) gpx file with lat/long, elevation and time. wanna calculate speed... ...