Tagged Questions

The time rate of change of the position of an object

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Relativistic velocity in Special Theory of Relativity [on hold]

Prove that, 0.5 m*v^2 , where m = M / (1- (v^2 / c^2))^0.5 ["M" is original mass, and "m" is mass with velocity] doesn't equal to the the Kinetic Energy of a particle moving at relativistic velocity. ...
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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 ...
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Clarification of the physics involved of an orbiting body in a circular orbit

I am writing a physics simulation program to simulate a body orbiting a planet but I am a little confused about the physics involved and would like some clarification. To simulate gravity I am using ...
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Pressure-Velocity relation at a point in a flow

How can we relate pressure and velocity at the same point in a fluid flow? Why does pressure decrease with increase in velocity?
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How to calculate the final velocity of object with variable acceleration? [on hold]

Initially, an object has a velocity of 0 m/s and acceleration 8.44 m/s2. After traveling 500 km, its acceleration is 9.81 m/s2. How would you calculate the final velocity of the object?
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Why do we need displacement? [closed]

In practical life we see objects not actually moving on same way as of displacement,They cover distance. While studying physics why do we study displacement and velocity. Is there any practical use ...
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Intepretation of area under velocity-time graph for a bouncing ball

A typical velocity-time graph for a bouncing ball is shown below. I understand that the ball starts from rest at $t=0$, then it accelerates downwards and hits the floor at time $t_1$. Between time ...
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Equation for a physic theory [closed]

There is a theory that state and explains why everything on earth (or on a place with same force of gravity) falls at the exact same speed in vacum. What's the name of that theory, who came up with it ...
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Projectile motion velocity [closed]

If a projectile breaks into two pieces at the highest point of its trajectory and one of them retraces the same path, why will that piece have the same magnitude in velocity as the whole projectile?
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Derive the velocity-additon formula from the Lorentz transformation

In a Euclidian world the sum $s$ of two velocities $v$ and $u$ is so such that $s = v + u$. However, in the world of special relativity that's not the case. Instead, the velcity vector sum $s$ is ...
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Rate of Acceleration of an Object Pulled by Magnetic Force

Gravity on earth pulls objects toward it with an acceleration of 9.8 m/s/s on Earth until the object reaches it's max potential free fall speed. (I call this terminal velocity though I think that this ...
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Why does objects with zero acceleraton move?

My question is, if we apply a force on an object to move it with a constant velocity, of course it will move. But what I don't understand is, why will it move? From Newton's law F=ma and in this case ...
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How can we find velocity, acceleration etc, of a revolving particle with respect to an observer inside the circle(not at center)

A particle is revolving in horizontal a circle of radius $R$ with constant speed of $|\vec{v}|$ and constant angular velocity $\omega$. There is another observer standing inside the circle, at a ...
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A question in Special Relativity

In books the equation for length contraction is derived by supposing that the velocity of the spacecraft is the same for both observers. So the question is that, is the velocity really the same for ...
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NB:I am not asking an answer for the question quoted. I had this question given in my book: A ring of radius $R$ rolls on a horizontal ground with linear speed $v$ and angular speed $\omega ... 0answers 25 views What is the relationship between the velocity of an object and its Sound Intensity Level in an inelastic collision? Assuming the mass, acceleration, and height of the dropped object are constant and the area of the measured sound wave is constant, would the relation be linear, exponential, logarithmic, square root ... 2answers 52 views Velocity of approach of a beam of light and a moving object I came across a problem on Brian Greene's course on Special Relativity. (http://www.worldscienceu.com/courses/6/elements/TnRUSU) From George's perspective, how fast does a beam of light approach ... 2answers 35 views Save a falling person by nullifying their mass or reversing gravity [closed] Let's say you have the superpowers to manipulate matter, mass and gravity. Imagine a person falls off a plane, flying few kilometers above the air, and they are about to get splattered onto the hard ... 6answers 4k views When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it? Consider these two situations when driving on a long straight road uphill: Starting at a high velocity$v_h$, which the car is able to maintain. Starting at a lower velocity$v_l$, and then trying ... 2answers 83 views Convert an equation for acceleration into one for velocity A sledge is pushed in a straight line. Assume surface is smooth. When the sledge is x distance away from the start the magnitude of its acceleration is given by$0.08e^{-4x}$and is going in the same ... 2answers 122 views Orientation of a rocket going in a circle? This problem is from my physics homework: A rocket is moving at constant speed in a perfect circle in deep space, far away from any planets or stars. The diagram below shows the circle the ship ... 3answers 89 views Difference between$|d{\bf r}|$and$d|{\bf r}|$What is the difference between$|d{\bf r}|$and$d|{\bf r}|$and why are both of them not always equal to each other? My question might seem stupid to some and will probably get downvoted but I have ... 1answer 47 views Is the car/wall comparison valid for speeds close to$c$? [duplicate] At school, people commonly think about momentum and conservation of energy using the example of a car collision. A common phrase is "Do not try to think of two objects moving, think of one moving at ... 3answers 1k views Does a moving object curve space-time as its velocity increases? We always hear how gravity bends space-time; why shouldn't velocity? Consider a spaceship traveling through space at a reasonable fraction of the speed of light. If this spaceship, according to ... 1answer 97 views Kinematics equations of motion find x position in 2D from height I have a question and I thought of 2 possible ways to answer it however the resulting answers are different which means I must be doing something wrong in my calculations. All the below happens 2 ... 1answer 80 views A particle in a 1D box: what is the meaning of velocity? In the box$x = 0$to$x = L$,$V = 0$, and for$x < 0$and$x > L$,$V = \infty$(infinite potential well). The eigenvalues of the Hamiltonian are: $$E_n = \frac{n^2 h^2}{8L^2} \, .$$ Since ... 2answers 93 views Sum according to a function - composition of velocities An observation more than a question. Take any function$f$(additional hypotheses may follow) and evaluate it on any two points$x_1, x_2\in\mathcal{D}_f$. Define then the sum of these two points as ... 1answer 25 views Velocity change of air down a cone? Does the velocity of fluids(specifically gasses) change when traveling down a cone from the wide opening to the narrow opening? If so, is there an equation used to calculate the acceleration or ... 2answers 604 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 ... 3answers 55 views Velocity and acceleration with variable friction If you have a body on a table,with a velocity$u_0$, going from a non friction area to a friction area, how do I find the function for velocity and acceleration due to the variable friction force(T). ... 8answers 7k views Why does a free-falling body experience no force despite accelerating? Note: For the purposes of my question, when I refer to free fall assume it takes place in a vacuum. From my (admittedly weak) understanding of the equivalence principle, falling in a gravitational ... 2answers 2k views Calculate speed from accelerometer I am trying to use my accelerometer on my mobile device (smart watch to be specific) to calculate a persons arm swing speed. The data returned from the accelerometer is in$m/s^2$. Since the ... 2answers 35 views Calculating the drag force provided by a laminar flow [duplicate] If I drop a ball into viscous fluid (e.g. oil), by calculation I know that the fluid flow is laminar. So which equation do I need to calculate the drag force provided by fluid? The drag equation, ... 1answer 53 views Angular velocity relative to different frames In Goldstein it is said "It is intuitively obvious that the rotation angle of a rigid body displacement, as also the instantaneous angular velocity vector, is independent of the choice of origin of ... 3answers 52 views How to figure out the height it would take for an object to reach terminal velocity? I'm trying to figure out how high an object would have to be dropped to reach it's terminal velocity. Specifically if an object had a terminal velocity of 520 mph, how would I figure out how high it ... 1answer 110 views Are we all moving at$c\$? [duplicate]

Is it true to say that all matter in the universe is travelling with velocity c through spacetime, but that for baryonic matter most of that velocity is through the time dimensions rather than the XYZ ...
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How to tell if area is displacement or distance?

why is it not called "velocity v. time"? how do you know? If the y-value can be either positive or negative, the direction is then indicated. i think this is why it should be called velocity but ...
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Can we escape Earth's gravity slowly?

I had a recent conversation with my girlfriend, who is a physics grad student. She was kind enough to listen to me rant about an idea concerning escape velocity. Unfortunately, I am still thinking ...
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Would the terminal velocity of a roller coaster train differ on the track from if it was free falling through air?

I'm working on a video about roller coaster science and I'm currently trying to figure out an average roller coasters terminal velocity going down a drop. All I can really do is fill in the ...
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If two objects have all the same conditions except different masses. Will their terminal velocity be different?

I can't seem to find a straight forward answer to this. I really just want to know if changing mass of an object affects the terminal velocity. If two objects of the same dimensions except one had ...
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2D aerofoil fluid analysis - find velocity ratio

I just wondered if you could help me out on this fluid mechanics question? I have worked through it myself but am very unsure of my answer (not yet found the pressure difference) the question is ...
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Question about rain when an object is moving

So here's the question: A train window is 1 meter high and 10 meters long. A raindrop rolls down the window at a vertical speed of 5 meters per second(when stationary). If the train is moving at 30 ...
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Factors on which Coefficient of restitution depend

What are the factors on which coefficient of restitution depend? What is the reason for more coefficient of restitution of two glass balls (0.95) than for two lead balls (0.20)?
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Is escape velocity really a velocity?

The term escape velocity is quite common to us. But we know velocity is a dimension dependent on the direction. But the escape velocity has same value irrespective of from where it is thrown from the ...
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Gravitational “acceleration” and frequency change of a photon?

For massive particles, force translates into acceleration which again is a change of the velocity vector in direction and/or magnitude. For a photon, the velocity magnitude cannot change, only the ...
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Symmetry considerations in Plane Poiseuille Flow

I'm taking a first course on fluid dynamics, and I have this (sort of) conceptual question that's been nagging me for a moment now. I can completely follow the mathematics behind the derivation of the ...
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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 ...
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Kinetic Energy and reference frame

Two space ships A and B moving through space in the same direction. Space ship A moves 2m/s faster than B, its weight is 1kg and it has a 2 Watt engine. It is accelerating with full power for one ...