The time rate of change of the position of an object

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3answers
125 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 ...
2
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2answers
225 views

Mathematical model for this graph of a simplified binary star system?

Unnecessary background for question: I had a school assignment asking us to relate a quadratic equation to a real life example relating to our future dream career, making sure to express the accuracy ...
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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{\| ...
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1answer
365 views

Deriving the group velocity of a wave produced by some basic cosine waves with unequal amplitudes

Consider some basic cosine waves of the form ${E_i} = {E_0}\cos ({\omega _i}t - {k_i}z)$ with different amplitudes, frequencies and phases. We know a combination of such waves could result in a wave ...
4
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2answers
2k 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
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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
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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 ...
2
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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
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1answer
255 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 ...
4
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1answer
3k views

Terminal velocity of two equally shaped/sized objects with different weights?

I've tried doing research on this and there are some similar questions. However, they have slightly different scenarios and to make sure I understand things perfectly, I wanted to word it into my ...
3
votes
1answer
527 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
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1answer
136 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 ...
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3answers
1k 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 ...
2
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0answers
163 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
315 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
225 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 ...
2
votes
2answers
195 views

How do you travel in a circular orbit around a massive body?

I am trying to figure out how an object could achieve a perfectly circular orbit. Given a mass for the planet or other body the object is orbiting and a distance from the center of mass, how fast ...
0
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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 ...
2
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2answers
976 views

Average velocity = Arithmetic Mean

I am having trouble grasping how the average velocity of a particle between an initial position and final position equals to the arithmetic mean of the initial velocity and the final velocity when the ...
0
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1answer
465 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.
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4answers
5k views

How can an object with zero acceleration move?

My physics text has a problem in which it is said that a person moves a block of wood in such a way so that the block moves at a constant velocity. The block, therefore, is in dynamic equilibrium and ...
0
votes
3answers
518 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?
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3answers
149 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 $\vec F \propto \vec v$ ...
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4answers
891 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 ...
-9
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3answers
188 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
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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 ...
0
votes
1answer
837 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 ...
1
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0answers
62 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 ...
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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
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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
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1answer
91 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
177 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
211 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 $r$, ...
1
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0answers
116 views

Is there any place you can safely skydive without a parachute?

While trying to explain to someone how a kitten walked away from a fall from a skyscraper I got to wondering if there's any place a human could do that and I find myself out of my depth. The only ...
4
votes
4answers
8k 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
812 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
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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
205 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... ...
4
votes
2answers
100 views

What's the physical difference between the quantities $\langle v_{i}v_{j}\rangle$ and $\langle v_{i}\rangle\langle v_{j}\rangle$?

What's the physical difference between the quantities $\left\langle v_{i}v_{j}\right\rangle $ and $\left\langle v_{i}\right\rangle \left\langle v_{j}\right\rangle $? Where $\left\langle ...
-1
votes
1answer
139 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 ...
-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 ...
-1
votes
1answer
264 views

Acceleration, velocity and speed

It is given that acceleration is constant, so can we infer that average speed and velocity are the same?? Moreover, circular motion is out of the question, as the function of x(t) where ...
2
votes
4answers
645 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 ...
1
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3answers
349 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 ...
0
votes
3answers
394 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 ...
2
votes
1answer
8k views

Need help with the position of a particle in a velocity-versus-time graph

I am having trouble with a velocity-versus-time graph. I recently took a Physics test that asked this question: The graph shows the velocity versus time for a particle moving along the $x$ axis. The ...
2
votes
1answer
825 views

Kinematics with non constant acceleration

A particle experiences an acceleration described by $$ a=kx^{-2} $$ where x is the displacement from the origin and k is an arbitrary constant. To what value does the velocity v of the particle ...
1
vote
2answers
95 views

Gravity mitigated by velocity regardless of mass?

We know that a small object moving fast enough can pass by a planet and escape its gravity. Would this be (theoretically) true in reverse? Meaning a planet moving fast enough past a stationary smaller ...
1
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1answer
91 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 ...