Questions tagged [velocity]

The time rate of change of the position of an object

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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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What is rate of heat produced in terms of radius $r$ in viscous liquid under gravity?

what is the dependency of the rate of heat produced in terms of radius $r$ after the drop attains terminal velocity when A small ball of radius $r$ is falling in a viscous liquid under gravity? My ...
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How does the size of the hole affect the exit velocity?

I took water bottles and drilled several different sizes of holes on the bottom. During the experiment, I found that the water bottle with a smaller hole takes a lot longer time to leak than those ...
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Kinetic energy of an object

We know that motion is relative. So let an object(o) be moving with a certain velocity with respect to an object (A).If another object (B) is moving with respect to (A) at a given moment and they ...
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What is the net force on an object which is moving with a constant velocity? [closed]

Imagine a toy car moving with a constant velocity. By Newton's second law of motion we can see that $F=ma$ and, since there is no acceleration, the net force is zero. But still we can experience a ...
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10answers
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Why does a free-falling body experience no force despite accelerating?

Note: For the purposes of my question, when I refer to free fall assume it takes place in a vacuum. From my (admittedly weak) understanding of the equivalence principle, falling in a gravitational ...
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1answer
196 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 ...
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How does the orbital radius affects the orbital velocity

I have a question says that "If the orbital radius of a satellite increase four times the orbital velocity will be ..." and the answer is that the velocity will be doubled !! We studied that orbital ...
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1answer
172 views

Is this Question correct? Newtonian Motion - Relative Motion of Rain

There is a question in a textbook which states: "A cyclist is riding north at 12km/h when it starts to rain. The rain appears to be falling towards her at an angle of 10 degrees relative to the ...
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4answers
166 views

What does a negative acceleration mean? Is the object slowing down, changing direction, or both?

I am confused about such things as negative velocity, acceleration, and displacement and what the negative indicates.
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Sign conventions for relative velocity problems

I am having trouble solving relative velocity problems because I can't seem to understand the sign that goes along with the velocity of different objects. $$ v_{ac} =v_{ab} + v_{bc}. $$ How do the ...
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What is the correct formula for relative velocity?

I have consulted byjus.com, HC Verma and Khan academy, all are saying different. byjus and HC Verma book is saying that formula for relative velocity is $V_a +V_b$ but in Khan academy they are telling ...
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How do you calculate the speed of air when it fills a vacuum of 1 cm³?

At different heights, atmospheric pressure is different. If a vacuum was created of say 1 cm³, how would i calculate the velocity of air filling it back in. The adjacent layer of air would obviously ...
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If velocity for an interval is zero then is acceleration also zero throughout?

We know that if velocity is zero for an instant, then acceleration need not be zero (a simple example of which is a ball thrown upwards.) But if velocity is zero for an interval, will acceleration ...
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A beginner's question on time dilation [closed]

I have just started understanding relativity so the question might look absurd. I know that the faster we move through space , the slower we move through time. But I haven't understood it fully. I ...
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2answers
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Is motion smooth? [duplicate]

It's obvious that for every particle velocity is smooth i.e it cannot undergo sudden finite change in its position in infinitisiminal time. Similarly any particle's velocity cannot undergo a change ...
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1answer
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Radial component of velocity at extreme distances

Suppose I am given that a planet's position with respect to some star is of the form $\textbf{r} = r\textbf{e}_{r}$. Then of course $\textbf{v} = \dot{r}\textbf{e}_{r} + r\dot{\theta}\textbf{e}_{\...
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What does it really mean by “faster flow, lower pressure”?

My primary school physics textbook trys to brainwash me with the idea that a region in a fluid with fast velocity (often) has lower pressure than a region that flows slowly. Examples of this include ...
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1answer
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How do u get Eq3 from Eq2&Eq1 [closed]

I keep getting the wrong results by subbing eq1 into eq2 It’s from Kleppner’s an introduction to mechanics 2nd edition
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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?
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Four-velocity vector of light

Please note that my question is not a duplicate, it is not about the speed of light, my question is only technical about the four velocity vector for light, its definedeness, value and constantness. ...
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4answers
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Does $j=\rho v$ hold in quantum mechanics?

Let's consider the current of probablity $\vec{J}(\vec{x},t)$ associated to a particle of mass $m$ with wave function $\psi(\vec{x},t)$, given by $$\vec{J}(\vec{x},t)=\frac{i\hbar}{2m}(\psi \nabla\...
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Choosing motor speeds for an omnidirectional robot given desired linear and angular velocity

Below is an example of an "omnidirectional robot" with four wheels. Each wheel has rollers on it so it can only exert a force along the line parallel to its face, coincident to the ground, and ...
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86 views

Do objects move in 2 directions at once?

If a velocity vector of an object can be divided into an x and y component relative to a second object's position, and both objects have gravity that attracts both objects to each other. We then know ...
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Finding tangential and normal velocity from a curve [closed]

How do you find tangential and normal velocity from a curve? I know how to find dy/dx, but I have no idea how to obtain ut and un and dv/dt.
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1answer
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Projectiles with unequal initial velocities, purely horizontal

If projectiles $A$ and $B$ are projected horizontally with different initial velocity from the same height, then both $A$ and $B$ possess the same vertical component of velocity, at any instant. ...
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2answers
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Do faster moving projectiles make larger penetration holes? [closed]

When it comes to shooting guns, a bullet of a certain size will make a certain size hole in the paper or wood target. A $.22$ bullet makes a pea size hole regardless of if its shot out of a pistol ...
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1answer
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How two cars are getting at the same point of the road (obstacle, cyclist, another car parked on a small part of the road) in the same time? [closed]

You have an ordinary road, two ways. You are driving on the right part of the road and you see a person walking on the same part 400m away, you have to slow down or to accelerate because from the ...
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1answer
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Relativistic Subtraction of Speeds

The formula for relativistic addition of speeds is well-known; say, if you were to have two objects travelling at each other at speeds of $v_1$ and $v_2$ (as measured by an outside observer), the ...
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1answer
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Scale diagram confusion

I’m familiar with scale diagrams where three forces act upon an object and trigonometry is used to find the resultant force, but I’ve come across questions that use units of velocity instead of force. ...
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Waves velocity for a standing wave of a string

I have done a laboratory experience to determine the speed of propagation of a wave in a vibrating magnetic string. To calculate the frequency (f) of oscillation I used an oscilloscope that calculated ...
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General relativity: For massless particles, is the momentum and velocity 4-vectors equal?

I am following Carroll's GR book. He explain that it is convention to parameterize geodesics of photons by a parameter $\lambda$ such that $$p^\mu ~=~ \frac{d x^{\mu}}{d \lambda}.\tag{3.62}$$ But ...
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Why can we parameterize a null geodesic such that its velocity is four-momentum? [duplicate]

One principle in general relativity is that the wordlines of massless particles are null geodesics. It also seem to be a commonly stated fact (for instance see eq. (3.62) in Section 3.4 of Carroll's ...
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How is final velocity negative when acceleration is in positive direction?

When a body starts from rest and starts accelerating in positive direction and moves certain positive distance, its final velocity is given by : $$v^2 = u^2 + 2as$$ Solving it gives two values of $v$, ...
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60 views

Speed of light as the maximum speed and movement course

Assuming we have 3 objects d,e,f moving on the same line while e is stationary, d is moving to the left at 'almost speed of light' and f is moving to the right at 'almost speed of light'. What is the ...
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Forces, gravity, and mathematics: simulating skateboard position as a function of knee bends in a half pipe

How would a physicist explain, perhaps with the aid of a diagram, how kinetic energy in the knees is converted to kinetic energy in a skateboard as a skateboarder with little initial velocity manages ...
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Frictional losses in flexible tubing with multiple branches opening up to a large tank

I am working on designing an experiment where I will be creating a wall-jet flow where the wall is a rotating wing. After some thought I realized I need to estimate the pressure losses due to the pipe ...
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1answer
89 views

How does acceleration affect time dilation and length contraction?

I just studied SR and I understand how velocity affects time and length; how do they evolve during the process of reaching a certain velocity?
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7answers
105 views

Is there centripetal acceleration with velocity of 5 m/s?

So if an object is moving at $5\ \mathrm{m\ s^{-1}}$ in a circle, is it accelerating? Me and a friend are having a conversation about this.
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Derivation of Lagrange's Equation [duplicate]

So I was going through the derivation of the Lagrange's Equation given in Goldstein. And I have doubts about some of the steps. I would appreciate some clarifications on them. First: $$ \frac{d}{...
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2answers
285 views

Relationship of a velocity vector in an inertial and rotating reference system

Sorry I can't write in latec, so I'm adding an image here. I don't understand how this transformation has been derived. $$ \frac{\mathrm d}{\mathrm dt}r_e = \left(\frac{\mathrm d}{\mathrm dt}+\,\...
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1answer
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Linear and angular speeds of a train

I am using Radar sensor in a train. Sensor is in the front part of the train to detect object and avoid collision. It needs vehicle motion data to calculate objects longitudional and lateral speeds....
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1answer
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Are there any formulas that calculate the stopping distance of a car on different surfaces that include deceleration?

I already found the formula $d = v^2/2\mu g$ where '$v$' is for velocity, '$\mu$' is for the coefficient of friction between the tires and the road surface, and '$g$' is the acceleration of gravity. ...
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What happens to velocity when Time equals zero?

I am not formally educated in Science but natural questions have always intrigued me.The way I put it is that I am married to Commerce but Science has been a childhood love. Now I have this very basic ...
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1answer
424 views

How to derive the law of velocity transformation using chain rule?

I know there is a straightforward way to derive the law of velocity transformation in Special Relativity by just dividing $dx$ on $dt$. But I am interested here to apply the chain rule and see how to ...
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There are two velocities on the sphere. How to sum them on the sphere?

As shown in the figure, there are two velocities on the sphere, one is the velocity along the meridian direction, the arc length is its size, the other is the velocity along the equatorial direction, ...
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2answers
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What's meaning of velocity of electron? [closed]

How do we define velocity of microscopic particles at small scales. As for macroscopic particle we can scale the distance travelled by object. But this is not the case with electron. Still, while ...
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Independence of position and velocity vector [duplicate]

Hi I am a mathematics student with an interest in Physics. In our Physics elective our prof. said if $\vec r$ denotes the position vector then the velocity vector $\vec v = \vec {\dot r} $ is ...
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1answer
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Spring mass system

While solving some spring block questions one doubt came in my mind ..is it possible to calculate maximum velocity of a point between two springs of different force constant attached to a block of ...
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1answer
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Hyperbolic motion with non-zero initial velocity

The equations of hyperbolic motion in a single spatial direction with initial velocity of zero are pretty easy to find given a bit of googling, such as in this answer. And while I'm too rusty at ...