The time rate of change of the position of an object

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1answer
66 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 ($a_c$) ...
1
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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 ...
3
votes
2answers
114 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
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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 ...
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
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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 ...
12
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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 ...
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, ...
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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 ...
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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 ...
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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?
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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 ...
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 ...
1
vote
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 ...
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 ...
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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)
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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
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0answers
47 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 ...
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 ...
0
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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
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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
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2answers
137 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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4answers
72 views

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

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 ...
0
votes
2answers
60 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
82 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
votes
1answer
124 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
61 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 ...
1
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0answers
23 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
37 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
22 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
41 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
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 ...
1
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1answer
46 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 ...
1
vote
4answers
104 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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votes
1answer
32 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 ...
2
votes
0answers
307 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
votes
1answer
57 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
vote
1answer
71 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
135 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
53 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
0answers
21 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 ...
0
votes
1answer
73 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 ...
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 ...
0
votes
1answer
62 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 ...
-1
votes
3answers
71 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. ...