The time rate of change of the position of an object

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116 views

Instantaneous velocity is slope of displacement-time curve?

I have a toss-up question that I'm not sure how to answer. Here it is (true or false): The instantaneous velocity at a particular time is the slope of the displacement-time curve at that position. ...
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1answer
316 views

Physical Meaning of Divergence of Convective Velocity Term

When taking the divergence of the convective velocity term, I get the following: \begin{align} \nabla\cdot\left[\mathbf u\cdot\nabla\mathbf u\right]&=\frac{\partial}{\partial ...
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2answers
884 views

Derivation of the average Velocity formula with constant acceleration (using calculus)

I have been looking at $$ v_{avg} = \frac{v_{i} + v_{f}}{2}, $$ when the acceleration is constant, where $v_i$ is equal to the initial velocity and $v_f$ is equal to the final velocity. How can ...
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1answer
2k views

How can I calculate the speed of an object knowing its horizontal and vertical velocity components?

Let's say a ball is thrown and it experiences typical projectile motion (moves in a parabolic arc etc.) and the only information we know are the equations for the horizontal and vertical components of ...
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1answer
179 views

A question about finding average velocity and average acceleration

I have trouble understanding the following problem's answer: Which of the following relations are true for any arbitrary motion in space? (a) $v_{avg}=\frac{r(t_2)-r(t_1)}{t_2-t_1}$ ...
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1answer
207 views

Displacement of an object due to opposite and equal forces acting at different times?

This question is about mechanical waves in solids, the speed at which forces propagate through solids, and the displacement that might occur due to unequal starting times of equally sized forces. ...
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1answer
99 views

Special relativity: circumventing velocity-addition formula

Two spaceships approach an observer from an equal distance and from an opposite direction with an equal speed $v$ in the observer's intertial reference frame $O$. The speed of a spaceship in the ...
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1answer
51 views

Knock out drum sizing for 10 times velocity reduction

How can I size a drum such that the velocity is reduced by 10 times inside the vessel. My velocity in the pipe entering the drum is 9.77 m/s. Velocity inside the drum should be 10 times less than 9.77 ...
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1answer
100 views

What is the speed of light from a star moving towards a observer.? [duplicate]

We can say that in vacuum speed of light is constant. But if the star is moving with a certain velocity does it add that velocity to the velocity of photons emitted out of that star?
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2answers
1k views

Help explain how direction change relates to acceleration [duplicate]

I was doing some simple harmonic motion problems and I came across this picture describing the position, velocity and acceleration of a linear oscillator. At the moment in time when v is 0 the ...
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1answer
52 views

Why is work not related to velocity?

A very simple question; why does it cost me more energy to very slowly lift a mass $m$ over my head compared to very fast? The definition of work does not state anything about velocity, only the ...
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4answers
2k views

Experiment - Measuring final velocity of a parachute

I'm working on a project that involves a scale parachute. It is vital for the project to get a good measurement of the speed it has when it lands. We still haven't built the parachute, but we need a ...
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1answer
62 views

Constant speed in curved space

Suppose a spaceship is travelling in the Schwarzschild metric. An observer at infinity sees the spaceship moving at constant velocity. What does this mean? Does it mean that: \begin{align*} ...
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1answer
896 views

Speed distribution in 1 dimension

In 3D, the maxwell velocity distribution is: $$f = \left(\frac{\alpha}{\pi} \right)^{\frac{3}{2}} e^{-\alpha v^2} d^3 \vec v$$ To get the speed distribution in 3D, we simply expand $d^3\vec v = 4\pi ...
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1answer
355 views

Spinning theoretical object moving faster than the speed of light [duplicate]

Let's say you have the Earth, or any celestial body, spinning as it is. What if you build a tower from the surface, and extended it out into space. If it was built far enough, could the furthest end ...
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1answer
2k views

Calculating the energy of an electron given the wavelength

Okay, so I know that the wavelength of an electron is 5e-7m and I am asked to calculate its minimum velocity and hence minimum energy. Calculating the minimum ...
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2answers
143 views

Final position of an object after aplying several horizontal forces [closed]

I'm given an object with a starting position. Several horizontal forces are applied to this object one after the other for different amounts of time. How can I determine the final position $x$?
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1answer
146 views

Velocity in the lift equation

What exactly is the nature of the velocity in the lift equation? I have read that it is the velocity of the aircraft, and I think I have read that it is the relative velocity of the air to the ...
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1answer
468 views

Using the Maxwell-Boltzmann distribution function to find specific molecule speeds?

I've been looking for problems to practice on this topic and found a problem asking to use the Maxwell-Boltzmann distribution function to calculate the fraction of Argon gas molecules with a speed of ...
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1answer
276 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. ...
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1answer
103 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 ...
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2answers
389 views

Escape Velocity question

I would like some help in understanding the derivation of the formula for escape velocity. Why does $t$ approach infinity? And why is $v(t)$ approaching zero? I know that $r(t)$ is infinite because ...
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1answer
481 views

How much runway does the space shuttle need to land?

A textbook question proposes the following scenario: NASA needs to plan emergency landing sites for the Space Shuttle (RIP). There are a number of things to consider. The shuttle touches down no ...
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1answer
165 views

Determining Orbital Velocity

Is there any way to determine the orbital velocity of a point around another stationary point, if I don't know the mass of either of the points but know the force that gravity exerts and the distance ...
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1answer
10k views

How to find maximum velocity

I stack a question about projectile question. The question was A projectile is being launched from ground level with no air resistance. You want to avoid having it enter a temperature inversion ...
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2answers
407 views

Horizontal Speed of Descending Parachute

I understand how to get the vertical (descent speed) of a parachute and its payload, but how could one find the horizontal speed/velocity of this parachute depending on the speed of the wind? (yeah I ...
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1answer
368 views

Measuring a Rod in Motion with two Synchronized Clocks

An explanation of special relativity I'm struggling with, goes like this: A rod traveling by a "stationary" observer has its length measured by use of two stationary synchronized clocks (synchronized ...
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1answer
958 views

Sound velocity in water

Conductivity, temperature, depth sensors are used by oceanography to calculate the velocity of sound at varying depths. These measurment values are used to comprise sound velocity profiles like the ...
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0answers
24 views

Difference between classic velocity and spatial velocity

I am reading a tutorial about a physics simulator I am using, and it has the following code (in C++, but not important): ...
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0answers
12 views

Force impact when lifting objects traveling at a relative velocity of 0

During a break my colleagues and I came up with the following Gedankenexperiment I would appreciate if you guys helped us find the solution for: Truck (weight 5t) traveling at 80 kph with a ...
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0answers
163 views

Portal 2 physics - one moving portal [closed]

A problem is posted and solved so many times on 9gag - till yet no good answer. The problem: you have two portals (one moving and one still standing). The one moving reach a still standing cube: what ...
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1answer
48 views

What is the physical significance of taking derivative with respect to proper time?

I would like to know if there is any physical significance associated with the derivative of a quantity with respect to proper time or is it just a mathematical trick. Since proper time is measured in ...
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0answers
25 views

How can a net force of 0 still lead to movement and how is movement possible with interaction pairs? [duplicate]

So I always thought of movement as interaction pairs. For example, I thought that a rocket moves by applying a force of hot exhaust gases, which then apply a reaction force back on the rocket ...
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1answer
37 views

At what velocity was this car traveling? [closed]

Throughout schooling we are given problems in which we are to solve for velocity, force, mass, etc. I have a real life situation in which I would love to solve these exact things. Please consider: Car ...
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0answers
24 views

How does a bikerider turn by leaning on one side? [duplicate]

I am trying to understand the following image: Could someone please help me understnding it. What I understood so far: Your angular velocity mutyplied by the impulse gives you the impulsemoment. By ...
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0answers
24 views

Retardation on a Conducting Object in a Magnetic Field [closed]

I cannot solve this question and I need help to understand the physics. The picture below says it all. What is the retardation (negative acceleration) on the conducting object with a mass of 2.5 kg's ...
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1answer
54 views

Tachyons and Lorentz velocity transformation

In general, is it possible to apply the Lorentz velocity transformation to a tachyon? I have tried to do so but the results seemed very illogical. Here's my attempt: suppose an evil spaceship named ...
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0answers
34 views

0G(No motion) scenario detection using Accelerometer and Gyroscope [closed]

I have a gyroscope and accelerometer which I am placing on the wheel of a bicycle to detect the 0G or standstill (when the bicycle exactly reaches to rest) of the wheel. I put the sensor at a R/2 ...
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0answers
22 views

Escape speed or Escape Velocity? [duplicate]

Which one should be the correct term escape speed or escape velocity? In one book it is given Speed whereas in another its velocity.
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0answers
33 views

Lining up fans in a row

Im new to this website, and not extremely educated in the world of physics. I have a very basic (mostly high school, some college) understanding of physics. That being said, I work for the fire ...
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1answer
75 views

Relativity: easy spaceship scenario. easy questions [duplicate]

Your spaceship is traveling at 1/2*c and you approach Bob's spaceship going -1/2*c in the opposite direction. Relative to you, Bob is going the speed of light, and of course he has a giant ticking ...
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1answer
38 views

Example of physical phenomenon with zero velocity at some point that does not correspond to an extremum [closed]

For many students (at least mine), the vanishing of the derivative $f$ at some point means that the function is maximal at that point. The cubic function $f(x)=x^3$ shows this is false. Students ...
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0answers
25 views

How to compute the speed of a cosmic ray from its energy? [duplicate]

How can you compute the speed of a cosmic ray from its type and measured energy? For example, if a cosmic ray were said to be a proton of 10 GeV, how would you compute the velocity of that cosmic ...
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2answers
189 views

How to find the height at which a projectile is launched from an angle? [closed]

I need guidance with the following question: A boat is $50.0m$ from the base of a cliff, fleeing at $5.00m/s$. A gun mounted on the edge of the cliff fires a shell at $40.0m/s$ and hits the boat ...
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1answer
32 views

Speed of different inclined plane [closed]

Assume friction-less, an object was release from the top, what is its speed at the lower end of the slope? I tried $v= \sqrt {2*9.0m/s^2*5m}$, but I doubt if it's a correct answer, any help?
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2answers
41 views

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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1answer
61 views

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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0answers
102 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 ...
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1answer
309 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 ...
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1answer
71 views

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 ...