The time rate of change of the position of an object

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2answers
23 views

Velocity selector and charge to mass ratio of an electron

I recently read that J.J. Thompson used a velocity selector to find the charge to mass ratio of an electron. Having learnt the principle behind the velocity selector, I see no relation between these ...
-1
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1answer
37 views

Can absolute speed of object be measured? [closed]

Let's say there are two objects in space - Station and huge non-transparent sphere. Sphere starts to move from station 5000 km/h. Inside the sphere, beam of light is produced in direction the sphere ...
5
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4answers
2k 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 ...
-1
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0answers
23 views

Calculus Based Physics Problem with Particle Motion [on hold]

Suppose the position vector for a particle is given as a function of time by $$\hat{r}(t) = x(t)\hat{ i} + y(t)\hat{j}$$ while $$x(t)=at+b \text{ and }y(t)=c(t^2)+d,$$ where $a=1.00\, m/s$, $b=1.00\, ...
1
vote
1answer
115 views

How are the theoretical properties of a gravity train linked to orbital properties?

Whilst perusing a question on WorldBuilding, a link was given to an article about Gravity Trains. Some of the answers on the question, and the Wikipedia article, state a travel time of 42 minutes ...
2
votes
2answers
777 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 ...
0
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0answers
28 views

How do I find the co-ordinates and speed of this particle on the x-y plane? [on hold]

I got this question from an old physics exam paper. I'm trying to use the kinematics equations to solve this question but the x and y co-ordinates keep confusing me. Here's the question: A particle ...
1
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4answers
70 views

How to explain to a child why can acceleration be positive or negative? [on hold]

I want to find out how can acceleration be negative? I have an answer and this answer is: $$a=\frac{v_f-v_i}{t_f-t_i} < 0$$ because $v_f < v_i$ where $v_f$ is final velocity and $v_i$ is ...
1
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1answer
41 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): ...
1
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1answer
327 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 ...
0
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2answers
45 views

is photon direction affected by source velocity? [closed]

let's suppose the red ball in the below image is an object with V' velocity, the car and the surface travel in V (0.5 c). based on relative velocity laws, the red ball will hit the green pointer ...
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1answer
46 views

Velocity of water from a certain depth

I was curious to know does water come out of a certain depth when there is a difference in pressure, and also if it does come out of a certain depth, at what velocity does it travel at? So, ...
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votes
1answer
56 views

Relative velocity of a boat traveling on a river [closed]

I am confused about relative velocity. So suppose a boat is traveling upstream on a river and a crate is dropped overboard. The boat continues to travel upstream for 60 minutes and reaches a ...
1
vote
1answer
38 views

Can empty space be a frame of reference to measure velocity?

I am wondering if there is only one object in the universe than does it make any sense to talk about its velocity. If empty space can be thought of as a reference to measure its velocity than it ...
0
votes
1answer
35 views

Time and velocity

Suppose two cars are traveling at a velocity of $c/2$ ($c$=speed of light) in two straight lines parallel to each other but in opposite direction in vacuum. Then what will a person sitting in one of ...
1
vote
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 ...
0
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2answers
31 views

(+)/(-) Acceleration & (+)(-) Velocity

Does a negative acceleration mean an object is slowing down? Does a negative velocity basically mean you are moving at an opposite direction? The sign is just direction?
2
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0answers
16 views

Why did they use two separate vectors to calculate the magnitude and angle of the initial velocity?

The question/solution are on the attached images. (It's dealing with projectile motion) I already understand how to work out part a, but I'm having trouble understanding why they used the final ...
2
votes
1answer
32 views

Ball Bounce Acceleration at the Point of Bounce [closed]

simple question but I wanted to confirm my approach of thinking about the problem. Question: A rubber ball is dropped from the fifth story of a building and free falls to the ground, after which ...
1
vote
1answer
31 views

How a wheel move on the earth?

I was wondering how a wheel move on the earth ,I mean if friction causes it moves so what causes it stops after a while without any pushing force? I think that the direction of the friction force is ...
2
votes
1answer
1k views

Drift velocity of electrons with changing area

What would happen with the drift velocity of a cylindrical resistor's diameter increases, with a given voltage between its terminals? According to the expression: \begin{align} ...
1
vote
4answers
84 views

if mass is dependent on velocity, and velocity is relative, how can we determine rest mass [closed]

If I'm not mistaken, $m=\gamma*m_0$ ($\gamma$ being the lorentz transformation) But $\gamma$ depends on velocity. How do we determine velocity if velocity is relative? If we are currently being flung ...
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1answer
27 views

Relative velocity

Question is from Barron's SAT subject test Physics "A flat railroad car is moving to the right at 5m/s. A person standing on the car throws a ball straight upward at 20m/s. If air resistance is ...
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0answers
192 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 ...
0
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1answer
50 views

Help with Gravity question

I need some help with this question from my homework. An Oort cloud comet moves on an orbit so eccentric that it can be well approximated by a radial straight line through the Sun. The comet starts ...
1
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1answer
49 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 ...
-1
votes
1answer
79 views

Position from velocity time graph [closed]

I have taken Calculus before but unfortunately no equation is given so I have to do it the old way. An object is at x = 0 at t = 0 and moves along the x axis according to the velocity-time graph ...
3
votes
1answer
44 views

Trouble with Simple Average Velocity [closed]

I have a super simple question on average velocity that either I am not setting up correctly, or is itself graded incorrectly in a huge online system used by thousands of students for a very long ...
0
votes
1answer
174 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 ...
0
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0answers
19 views

Time taken to cover a point object in a circular region

I'm assuming a finite width rotating beam with increasing width as it gets closer to the circular edge. I'm trying to find the time it takes the beam to cross a point object at some distance from the ...
4
votes
1answer
322 views

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 ...
0
votes
1answer
31 views

Does the velocity of steam affect the transfer of heat?

I am analysing a heat exchanger system which uses steam travelling through a finned tube to warm air. I am currently looking at reducing time lags in the system so as to raise the temperature of the ...
0
votes
1answer
61 views

What is meant by 'Phase velocity is $c^2/v$' [closed]

Is phase velocity $c^2/v$ or $v/2$? Is there only one phase velocity as indicated by the above formula? If yes then why is wavepacket said to be superposition of 'waves' whose velocity is termed as ...
1
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1answer
56 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 ...
-1
votes
3answers
69 views

Are all conserved scalars proportional to relativistic mass? [closed]

I have read in Rindler's relativity book that all scalars depend only on the magnitude of velocity of a particle and that are conserved are proportional to relativistic mass. ...
4
votes
1answer
11k views

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

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 ...
-2
votes
1answer
53 views

Objective velocity (Relativity theory) [closed]

Suppose that I have a velocity of (approximately) $c$. Then I decelerate with $c$ per hour for exactly one hour. Then I would know that I would be standing still in the end, because the decelleration ...
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1answer
46 views

Empty space and velocity

If there was a universe without anything in it except you in a space rocket how you would you know what your velocity if you kept the engine on?
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0answers
27 views

Calculating electricity used for weights on an elevator

Given an elevator with a motor driven by a power supply, torque ability and a pulley does it take more electricity to lift more people? I have some of the calculations but do elevators lift at a set ...
5
votes
5answers
314 views

Why is rapidity additive?

With the rapidity $\phi$ defined so that $\frac{v}{c}=\tanh{\phi}$, say you have 3 parallel moving reference frames $S$, $S'$ and $S''$ with a constant but different velocity/rapidity. If the ...
0
votes
1answer
29 views

Finding acceleration using components method

The problem I am working on gives me an initial velocity of 2[E15N] m/s and a final velocity of 4[E35N] m/s after 30s. I need to find acceleration so I create a right angle triange for both of these ...
1
vote
1answer
46 views

Difference between escape velocity and speed [duplicate]

What is the difference between escape velocity and escape speed , is their any error if we use them interchangeably?
0
votes
1answer
36 views

Having trouble understanding projectile motion [closed]

So, I learned about projectile motion in class a fe days ago, and am having trouble understanding. I main problem is seeing how velocity works in projectile motion. For example, why is the velocity in ...
1
vote
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 ...
0
votes
1answer
64 views

Question about acceleration & deceleration in real world?

have searched the net and am not satisfied with any answer I have found to calculate the following:- Here is an example just for reference. Suppose I can accelerate my car from 0-100km/h in 10s. That ...
1
vote
1answer
38 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 ...
2
votes
2answers
107 views

Velocity addition rule in special relativity

I just worked out a problem showing peculiarities of the velocity addition rule in special relativity. This was the statement for the problem: "Nefarious thieves flee the scene of their bank ...
0
votes
2answers
39 views

motion with constant acceleration question! [closed]

Consider a motorboat maneuvering on the surface of a lake, Is it possible for the boat to have accelerated motion in the x axis and unaccelerated motion in y direction?
1
vote
6answers
16k 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
1answer
43 views

Velocity of a liquid jet, coming out of a container

Think of a container which has a hole beneath it. And we have filled the container in height $h$ with a liquid of density $\rho$ and cross section of the hole $a$. (look at the pic) Then what is the ...