The time rate of change of the position of an object

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1answer
271 views

Finding an equation to solve for the velocity of a swimmer crossing a river [closed]

Where $\theta=45^\circ$, $d_1=200\:\mathrm{m}$, and $d_2=150\:\mathrm{m}$. I do not know how to combine the following equations: $$\begin{align} t&=\frac{d_1}{v_s\cos(45^\circ)}\\ ...
0
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1answer
34 views

Shock Absorber - Bus - Not Uniform

Imagine a empty bus/lorry travelling at high speed over the "speed brake", why is that only rear seat is heaved relatively high compared to the fron seat?
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2answers
429 views

How can I calculate the initial velocities of a set of objects with a consistent force?

I'm trying to figure out which object would have the largest time of flight when launched from a slingshot. To do this, I need the initial velocity. How can I calculate this if I know the mass and ...
6
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5answers
8k views

If an object moved 5 meters in a second, how can its velocity be 10 m/s?

I am reading the tutorial on physics classroom.com, and am at Meaning of Slope for a v-t graph. It gives data for an object experiencing an acceleration: This is the corresponding chart for the ...
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3answers
126 views

Question about relative speeds on a different “scales of perception”

I was kind of puzzled yesterday when thinking about this. If we observe an object moving away from us with 10m/s we would say the object is moving away from us really slowly But if we (humans, ...
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2answers
64 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
87 views

Finding the constant of gravity in a game [closed]

Minecraft is a game of mining where one digs and finds ore (to put it simply). the world is composed of "blocks" 3 dimensional cubes that have different "pictures" on them, that make them appear like ...
2
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2answers
465 views

What will be the velocity of a comet is falling to the Earth from infinity at the time of impact if Earth had no atmosphere?

What will be the velocity of a comet is falling to the Earth from infinity at the time of impact if Earth had no atmosphere? the comet is falling radially towards the earth. Will this velocity be ...
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0answers
44 views

Determining impact velocity over long distances [duplicate]

Everything I have found concerning impact velocity from a given height deals with constant acceleration due to gravity. I would like to know how to work in varying acceleration into the equation. So, ...
-1
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1answer
106 views

Displacement inside the moving Object

Suppose say a person is standing over the moving bike and he jumps while bike is moving, bike will move forward & person will land in same point at which he jumped, relative to earth position ...
3
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1answer
230 views

Does decreasing the length of the line between a harness and zip wire increase the velocity at which you travel?

My friend is an instructor at an outdoor adventure centre which has lots of zip wires. The instructor's harness has a shorter line that attaches to the zip wire than the normal harness does and she ...
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0answers
1k views

Find initial velocity when given max height of 100m [closed]

A ball is thrown straight up. The height of the ball above the ground in (m) is given by the function: $$h(t)=-5t^2 + vt + c$$ What is the initial velocity if you want the ball to reach a max height ...
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2answers
260 views

2 bodies separated by a rope [closed]

Say you have two bodies connected by a "weightless" rope, one hanging from a ledge on a pulley (classic pulley problem). If the body that is on the surface and being pulled by the object hanging ...
0
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1answer
97 views

Given Velocity formula and told to find acceleration, I need help please. [closed]

I tried to do this problem by taking the derivative and it did not get me the right answer. I also tried the Vdv=Ads integration and could not get the right answer. Please Help
1
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1answer
186 views

Determine orbital position after change in velocity

I am working on a satellite simulator for a project/game and I am stuck on this one bit of physics. So far I have a satellite that revolves around earth on a 2D plane following Keplerian motion using ...
2
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1answer
71 views

Is it possible to affect the trajectory of a black hole?

Basically is the black hole itself affected by the matter going into it? Does it either get pulled by gravity toward things or have its own velocity affected by matter that "impacts" it?
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5answers
3k views

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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3answers
251 views

According to relativity, can a statement be true and false in same time?

Say I write following statement on a paper: It's year 2014 at earth. Then I give it to my friend. My friend then starts to leave me and earth to outside with velocity of light. Einstein says the ...
7
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3answers
383 views

Does Super Mario physics work in reality? [duplicate]

This illustration summarizes my question: Please assume no air resistance (unless that makes a large difference). Here's what we concluded, but I could use both confirmation and also help with the ...
1
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2answers
166 views

Can a bullet leave a gun and tumble to the ground?

This question seems to have been asked a few times in different configurations, but none of them answer my variation. I've struggled to understand this for nearly 15 years and had conflicting answers ...
0
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1answer
1k views

Distinguish between instantaneous speed and instantaneous velocity

I encountered a line in my text book of physics that: Average speed over a finite interval of time is greater or equal to the magnitude of the average velocity. But instantaneous speed at an ...
0
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0answers
103 views

Graph of Lorentz force in function of angle between v and B-field?

I need to draw a graph of the magnitude of the Lorentz force in function of the angle between the velocity and B. Am i right in supposing this will be a sine wave?
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0answers
423 views

Gravity change as a function of time only

Is it possible to find how gravity changes with time? That is, height is not part of the equation. For example, $g$ can be expressed as a function of height that does not involve time with this ...
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1answer
83 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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3answers
142 views

Velocity vector for constant acceleration in newtonian mechanics

If the acceleration vector of an object remains constant, is there no change in the direction of the velocity vector? The question applies to any movements in classical physics.
2
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1answer
139 views

Speed of three objects falling with different masses

The following is the problem that I am working on. Three different objects each with mass $m_1<m_2<m_3$ is launched from the same height $h$ with three different angles $\theta_1 < ...
7
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2answers
2k views

Does velocity or acceleration cause time dilation?

What causes time dilation? Acceleration or velocity? I've seen multiple comments on this forum that assert velocity is the cause, but that doesn't seem right to me. You can't have velocity without ...
3
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2answers
526 views

Velocity and acceleration in SHM

Can velocity and acceleration reach maximal values during the SHM simultaneously? Can you explain why?
4
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3answers
248 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 ...
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1answer
363 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 ...
0
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1answer
882 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. ...
5
votes
3answers
299 views

Physical intuition for independence of components of velocity in derivation of Maxwell–Boltzmann distribution

Maxwell derived the shape of the probability distribution of velocity of gas particles by starting with just two assumptions. These are: The probability distribution is rotation invariant. The ...
4
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2answers
131 views

The velocity of a cloud?

I noticed an unusually fast moving cloud this morning. My questions: What is the average velocity of a cloud on Earth? What is the greatest ever recorded cloud velocity? What factors affect the ...
2
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2answers
148 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 ...
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3answers
263 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?
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1answer
137 views

Can the phrase “Terminal Velocity” be used to describe non-gravity situations?

According to Wikipedia: [Terminal Velocity] is the velocity of the object when the sum of the drag force (Fd) and buoyancy equals the downward force of gravity (FG) acting on the object. Since ...
2
votes
1answer
91 views

Can I express the heat flow of a fluid in terms of estabilshed characteristics of the velocity distribution?

If $\rho$ is the mass density of a fluid and $A({\bf v})$ is an function of the velocity, which is distributed according to $f({\bf v})$, we have an averaging process $A\mapsto \langle A\rangle:=\int ...
2
votes
1answer
491 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}} ...
2
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2answers
1k views

I don't understand the idea of perpendicular vectors being independent of each other?

So problem 71-75 is about vectors. The problem says: A river has a current flowing with a velocity of 2.0 meters per second due east. A boat is 75 meters from the north riverbank. It travels at ...
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1answer
207 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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2answers
271 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 ...
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0answers
24 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 ...
4
votes
1answer
369 views

Velocity of a viscous fluid through a tube

When a viscous liquid flows through a tube in a laminar flow, why is its velocity highest at the center? I understand the concept of shear viscosity and why the liquid in contact with moving plate ...
2
votes
0answers
97 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 ...
1
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1answer
633 views

Newtons Cradle, Collision Theory

It has come to the point in my computing program now where I have 5 swinging pendulums that are all modified at once by slider values. These values are drawn onto the from and passed through the class ...
0
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3answers
136 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
votes
2answers
298 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 ...
0
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1answer
105 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{\| ...
0
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1answer
545 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
3k 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?