# Questions tagged [velocity]

The time rate of change of the position of an object

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### Is the answer given in the option wrong? [closed]

The question is "An Object moves along a straight line. The graph illustrates how the acceleration of the object changes with time. The direction of the motion of the object changed only once, ...
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### Doppler shift from a moving reflector and source if only the relative velocity is known?

Suppose there is a device which is producing and listening to sound (sonar), a reflector is moving with respect to device and the velocity of reflector and device with respect to the air is not known, ...
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### How does the result of derivative become different from average ratio calculation?

Lets give an example. Velocity, $v=ds/dt$. If we know the value of $s$ (displacement) and $t$ (time), we can instantly find the value of $v$. But then this $v$ will be the average velocity. Now ...
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### Why does a charge need to have a velocity to experience force in a magnetic field?

While studying magnetism, I learned that force on a charged particle inside a magnetic field is $$\mathbf{F}=q(\mathbf{v}\times\mathbf{B})$$ where all symbols have their usual meaning, which implies ...
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### Motion formula gives correct answer but without formula gives wrong answer [duplicate]

Assume a body with initial velocity= 10 ms final velocity= 20 ms and acceleration= 2 ms , so the time to reach final velocity will be 5 seconds. If we try to find distance it will travel in 5 seconds ...
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### Why is velocity proportional to radius in a spherical explosion?

While doing problems on spherically symmetric explosions, I noticed I had been intuitively assuming that velocity scales linearly with radius of the "shell" under consideration. To be more ...
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### Why doesn't constant acceleration give me total displacement?

I started learning 1D kinematics and learnt definitions of constant velocity and constant acceleration. I thought that if a particle is changing its velocity uniformly then it has constant ...
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### Setting $u$ = escape velocity when calculating the maximum height of a thrown object

So, if I throw an object at some velocity $v$ at an angle θ, the maximum height reached by the object is $\frac{v^2\sin^2{\theta}}{2g}$ but, I know this isnt true. clearly in a weird way, the height ...
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### This model of friction implies the speed decays exponentially, but shouldn't it actually vanish within a finite amount of time?

A snooker player strikes the cue ball, so that it starts moving with constant speed $v_{0}$. We assume that spin plays no role in its motion. Due to friction between the ball and the cloth of the ...
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### How do mass and velocity relate to momentum? [duplicate]

So this is more of a clarifying question. A lot of online definitions state that momentum is a measure of how hard it is to stop or swerve an object, which makes sense. However, the formula for ...
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### Linear velocity on a circle

Consider a ball rotating around the z-axis with constant angular velocity $\vec{\omega}$, then the linear velocity $\vec{v}$ is given by $\vec{v} = \vec{\omega} \times \vec{r}$. It is easy to ...
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### What is the physical significance of this generalised potential?

Consider a generalised potential of the form $U=-f\vec{v}\cdot\vec{r}$ where $f$ is a constant. This potential should not contribute any internal forces between particles as \vec{F}=-\...
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### Where does "excess" energy go when a vehicle uses a lower gear to move at a given speed?

So I understand that a lower gear as advantageous when accelerating a vehicle or when driving up hill (e.g because you are having to accelerate against gravity). I know this is because of the ...
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### Is it possible to have a uniform speed but variable velocity in one-dimension motion?

Is it possible to have a uniform speed but variable velocity in one-dimension motion? I saw a lecture where teacher said that it is possible if particle changes its direction of motion 180$^\circ$. ...
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### In the formula for the conservation of mechanical energy, what does mean the velocity?

For example I have the formula: MEI=MEF mgh+mvi2/(2)=mgh+mvf2/(2), What does initial and final velocity mean?
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### How to calculate the final position of a particle under variable accelaration and its instantenous velocity?

I'm a first-semester physics student who was recently on a train. On a screen, it said the instantaneous velocity of the train was 176 km / h. We had 4 min left until our destination. I wanted to ...
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### Changing variables from $\dot{q}$ to $p$ in Lagrangian instead of Legendre Transformation

This question is motivated by a perceived incompleteness in the responses to this question, which asks why we can't just substitute $\dot{q}(p)$ into $L(q,\dot{q})$ to convert it to $L(q,p)$, which ...
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### Circle to Polygon & Circle to Circle Velocity Resolution

I current am working a 2d physics engine, but have recently hit some bumps in the road. Polygon to polygon collision and velocity resolution works without issue, but I am struggling to get working ...
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### Statistical independence of $x,y,z$ dimensions for Maxwell velocity distribution function

I have been looking into the derivation of the Maxwell speed distribution function as for instance given in https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution#...
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### In this conservation of momentum problem, where is the sign error coming from?

Say I have a particle travelling in the $x$-direction and breaking into two pieces: Conservation of momentum in the $x$-direction obviously gives: $$mv = m_1 v_1 \cos(30) + m_2 v_2 \cos(60).\tag{1}$$ ...
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### In $a = dv/dt$, is $a$ the net acceleration? [closed]

While going through the calculus approach to accelerate, we have, $$a = dv/dt,$$ I think, here, v and a should be in the same axis, is my process correct? in a planar motion in two dimensions, it ...
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### How does the distribution of floor choices of your co-passengers affect your time of arrival in an elevator?

Note: This is a wiki post. Suppose you are late for a meeting and you have to take an elevator. The floor choice of your fellow passengers influences how late you will reach your destination. If ...
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### Average velocity showing different results

I was solving a question, in which, a particle has travelled a distance $s$, with initial velocity $0$ and constant acceleration. So the equation of motion becomes, $$v = a t \tag{1}$$ and  v = \...
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### How does a seatbelt help in a car crash? [closed]

If you are in a car crash, you will likely have on a seatbelt because they are supposed to help you from getting injured/harmed. But, I don't think they are that much of a help. First of all, say you ...
1 vote
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### Determining star position and velocity to deduce closest approach?

I am trying to replicate the results found for Gliese 710's closest approach of ~0.05 parsecs in 1.3 million years approximately. I thought that by plotting the sun at (0,0) and using the stars ra,dec,...
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### Magnitude of Acceleration Vector when Speed is Constant

If I observe a change in direction of velocity, but not in speed: What does the acceleration vector look like? I am confused! The difference vector between two vectors of equal length A has a ...
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