The time rate of change of the position of an object

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2answers
375 views

How to achieve speeds faster than light? [duplicate]

So, I heard that all speed is relative. And that nothing can travel faster than light. Then I guess it is OK for a spaceship to leave Earth at 0.6c constant speed. And what if an other spaceship were ...
43
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6answers
6k views

If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?

Let's say I fire a bus through space at (almost) the speed of light in vacuum. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus toward the front, does that mean I'm ...
0
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2answers
45 views

Position, velocity and acceleration vs time graphs

I'd like to draw graphs of a vehicle and I have a position vs time table. I can set the points but how am I supposed to join them, straight or hyperbole ? If the object is accelerating which is yes ...
1
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1answer
106 views

Are velocity and acceleration smooth quantities?

My thinking: acceleration corresponds to a force which is instantaneous, so the acceleration of a rigid body can be rather spiky (non-smooth) velocity (angular velocity) describes the ratio of ...
2
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2answers
47 views

Does the position-time graph have to be a smooth function?

If at some time $t$ there were a discontinuity in the velocity-time graph, then the acceleration would be infinite at $t$. So intuitively, it seems that the velocity-time graph must be continuous. I ...
0
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0answers
74 views

Calculating travel time based on distance, velocities, acceleration, and jerk

Not much physics background so please bare with me. Say we have an object traveling on a straight line going from x to y. We know the starting velocity at x, the velocity when y is reached, the max ...
0
votes
1answer
36 views

How would you get the velocity in this problem? (and what did I do wrong) [closed]

This problem is supposed to be solved by using the conservation of energy but I do not really know how to solve it that way.
0
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1answer
43 views

How to average velocities [closed]

I have a body at motion and I need to calculate it's average velocity However all the data I got is 2 average velocities the first from the first half of the time of motion and the secon from the ...
0
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0answers
14 views

Finding the inner rotational velocity of a vortex incrementally

This is for improving accuracy in a prototype hydro design spreadsheet. Hypothetically: In a 6.6m tank, water enters tangentially at 0.575m^3/s with a velocity of 0.7m/s. The height of the resulting ...
2
votes
1answer
217 views

Lagrangian of Non-Relativistic Charged Particle in a Magnetic Field

I'm trying to derive the Lagrangian for a non-relativistic charged particle under the influence of a magnetic potential. I'm assuming that $F=-\textrm{grad}(V)$ and so by the Lorentz force we have ...
2
votes
1answer
62 views

Velocity of water column

If an air filled tube 5 km long with a diameter of 20 m was submerged vertically under water one end 5 km underwater and the other end at the surface, how fast would the water column rise if the ends ...
1
vote
1answer
38 views

In rotating frames, particles do not travel at constant velocity?

If we measure a particle's trajectory in a rotating frame of reference as $\vec x=\vec x(t)$, then $\frac{d^2\vec x}{dt^2}=0$ could be zero? I'm trying to explain why the Newton's first law of ...
1
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1answer
30 views

Special Relativity and Composition Law for Velocities with respect to an observer watching two objects moving away from a central point

So I understand that special relativity is all about the frame of reference and there is a lot to do with time dilation and how space-time is warped at velocities near $c$. So my question is what ...
1
vote
1answer
30 views

Particles velocities directly after an inelastic impact with a smooth frictionless surface

Let us consider the following situation where a dumbbell falls onto a smooth and frictionless surface. The dumbbell is formed of 2 particles, each of mass $m$, linked by a massless rod of length ...
3
votes
2answers
116 views

Rain drop sliding on car windshield

Problem Definition As shown in the figure below, an automobile is travelling horizontally in the rain with a constant velocity V. The windshield has a slope of θ. A raindrop with a mass of m, ...
0
votes
1answer
67 views

Calculate constant acceleration needed to reach terminal velocity at specific time [closed]

I'm trying to find a way to calculate a constant acceleration given the following: One dimensional motion. The only forces involved are the force ($F_a$) caused by a constant acceleration ($a_c$) ...
0
votes
1answer
106 views

Final Velocity of an object on Parabolic Curve

I decided to participate in a school challenge involving launching a marble off a curved ramp from a given height and determining the distance the marble will travel. I can no longer participate, ...
1
vote
0answers
73 views

How to calculate velocity of air through a pipe? [closed]

I was wondering if there is any equation that helps to calculate air velocity through a pipe? I cannot find anything although I did find that velocity of air (not in a pipe) can be found by: Is there ...
0
votes
1answer
24 views

Velocity of flue gas

I was wondering on how to calculate velocity of a flue gas which has a gas molecular weight of 28.1544, density of 0.0268 (lb/ft$^3$), temperature of 980˚F, specific heat of 0.2805 (Btu/lb-F), and ...
12
votes
4answers
1k views

Is the velocity with which molecules of the medium oscillate same as velocity of the sound in that medium?

I wanted to know that under sound field applied molecules of the medium oscillate with some velocity in the direction of sound propagation. Is this velocity same as velocity of the sound in that ...
1
vote
1answer
105 views

Objects travelling relatively to each other faster than light?

When we say that something is travelling a certain speed, it's really travelling that speed relative to the Earth. When saying the speed of anything, it is, for the most part, relative to something ...
1
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3answers
257 views

When a body accelerates, it gains (relativistic) mass; after stopping, is the (relativistic) mass different from before it started accelerating?

When a body accelerates, it gains (relativistic) mass $m$ according to the relation $$m=\frac{m_0}{\sqrt{1-(v/c)^2}},$$ where $m_0$ is the (rest) mass. But after it stops is the gained (relativistic) ...
0
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2answers
45 views

Problem with variation of velocity, doubt on the work energy theorem

I think I did not understand the use of the work energy theorem. Here is a situation I am confused about. Consider an object moving in the $xy$ plane with a constant velocity $\vec{v_0}$ at an angle ...
0
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1answer
52 views

Terminal Velocity in Water

Another question concerning classical physics. On Earth, the combination of air resistance and gravity interact in a way that creates the phenomenon of terminal velocity. Do other fluids (for example, ...
1
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1answer
2k views

Difference between Speed and Velocity

What is the difference between Speed, Velocity and Acceleration? Could any one describe it pictorially?. I am more over confused even after investigating many times. I am unable to relate myself ...
-1
votes
1answer
55 views

Error in deriving relativity velocity addition formula [closed]

$D$ is traveling at .995c with respect to $C$ who is traveling at .995c with respect to $B$ all in the same direction. We want to compute $D$'s velocity as observed from $B$. Note that the Lorentz ...
1
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1answer
22 views

Distance formula using initial velocity and acceleration

we know $S=ut+1/2at^2$. Now lets say my initial velocity $u=10m/s$ and acceleration be $a=5m/s^2$. In first second distance traveled $S^{_t=1}=10m$ as my speed is $10m/s$ and time is $1s$. In next ...
0
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2answers
45 views

Regarding Basic laws of motion

When a constant force is applied on body which is free to slide on a surface, does it move with a constant velocity after some time or does the velocity keep on increasing? Please explain it for both ...
1
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0answers
29 views

Direction of motion 1 [closed]

A man on a bike travelling east on straight road at 8km/h sees a car driving north at 60km/h. What is the apparent speed and diretion of motion of car to the cyclist?
1
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1answer
40 views

Calculate final velocity for vertical projectile with air resistance

I am struggling to figure out how to calculate the final velocity of a projectile that is shot vertically upwards and then let fall down again to the starting point. I can easily calculate this in ...
0
votes
1answer
47 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 ...
3
votes
3answers
115 views

How can we define a velocity for quantum objects?

I have a question about quantum mechanics: I know that velocity is defined as the change of position with time, $v = \frac{\mathrm{d}x}{\mathrm{d}t}$. In quantum mechanics, the position of a particle ...
0
votes
1answer
299 views

How do objects even move due to gravity?

I am an newbie general relativistic learner and I learnt that gravity is bending of space-time and since objects move in straight-lines but since its curved they follow curved movement through space ...
1
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1answer
29 views

Average Velocity? [closed]

May any one explain to me this problem.. A particle moves a distance x_1=20m to the east (+ve direction) in a time t_1=10s. And again to the east a distance x_2=40m in time t_2=20s. Find its average ...
14
votes
3answers
929 views

When passed, why does my car 'rock' on the highway when I'm stopped, but not when I'm moving?

I am the blue car in this scenario. If I am stopped on the highway and am passed by a car going fast (about 65 mph), I feel my car rock in the left/right direction. I think I understand why this ...
10
votes
4answers
5k 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 ...
0
votes
1answer
29 views

How do I find the average velocity within a time interval [closed]

A particle moves in one dimension, and its position as a function of time is given by x = (1.8 m/s)t + (−3.6 m/s2)t2. (a) What is the particle's average velocity from t = 0.45 s to t = 0.55 s? (b) ...
-1
votes
1answer
45 views

confusion regarding force applied at different angles and work thus done? [closed]

considering $f=1$ and $s=1$ in the work-energy theorem , $W= \cos(\omega)$ this shows that as we increase the angle we do less work for moving an object to the same distance. It also means that ...
1
vote
2answers
55 views

What's the nature of intraction between hydrogen atoms in the interstellar medium?

Interstellar densities are about 1 atom/cm$^3$. Do these atoms even move? If they do, why do they move? What would be their average speed? (Free expansion)
-2
votes
1answer
291 views

Something almost faster than light traveling on something else almost faster than light [duplicate]

Possible Duplicate: Travelling faster than the speed of light Double light speed Lets say that an airplane can fly at 4/5 of the speed of light, and I can run at 2/5 of the speed of ...
1
vote
3answers
8k views

Calculating car's acceleration from change in angle of hanging object?

The question essentially is based on a situation like this- A car has a small object hung from the cieling on a string (apparently at an angle of 0 degrees to the ceiling). The car is accelerating ...
1
vote
0answers
27 views

If mass increases as velocity increases, does gravity increase as well? [duplicate]

The way I understand it, velocity and mass are tied together with relativity. As I increase in velocity, I increase my mass until my mass is so great that it would take more energy than the entire ...
0
votes
1answer
31 views

Velocity of propagation of an EM field in vacuum

I am asked to find the speed of propagation $\vec{v}$ of an electromagnetic field, in a region of empty space. The magnetic field is described by $\vec{B} = B_0e^{ax}\sin{(ky-\omega t)} \hat{z}$. I ...
-1
votes
1answer
57 views

How to use Special Relativity in simple numericals? [closed]

So I was recently thinking about what an electron's velocity would be after it was accelerated through a potential difference of 1 V. Doing simple calculations like just dividing its energy (which ...
1
vote
2answers
129 views

Is escape velocity really a velocity (rather than a speed)?

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 ...
1
vote
0answers
48 views

What's the equation for the magnetic field created by a single moving electron?

Suppose we have an electron moving in a straight line with velocity $v$. My question is: What is the equation that describes the magnetic field generated by this movement. I'm unsure how to proceed ...
0
votes
0answers
34 views

Advection Operator shift in scalar product

Can someone help me with advection operator shifts? I can't figure out the rule for the shift inside of a scalar product. The terms $(u,(v\cdot \nabla)\delta v)_\Omega$ and $(u,(\delta v\cdot ...
0
votes
0answers
11 views

How to express Darcy velocity as a function of mobility and capillary pressure?

I have a problem with deriving a certain expression for the Darcy velocity of water, when we have a piston like displacement of oil with water. The expression I am supposed to show is the following: ...
0
votes
2answers
139 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
votes
1answer
40 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 ...