# Tagged Questions

The time rate of change of the position of an object

0answers
453 views

### Finding the terminal velocity of a magnet dropped in a solenoid

We have to find proportionality of the terminal velocity with the factors of the system: Plot: a small dipole(mass $m$) with dipole moment $\mu$ is dropped in a long solenoid (radius $r$, ...
0answers
20 views

### Velocity Profile of the Upper Atmosphere

Consider an Earth-Centered Inertial (ECI) frame in which the tangential (to Earth's surface) velocity is measured. Now consider obtaining constant average velocity profiles of the atmosphere as a ...
0answers
24 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 ...
0answers
105 views

### Deceleration of spherical particle in fluid

If I know the initial velocity of a particle entering a fluid, how can I calculate its deceleration over time ? What parameters would I need to know ? Viscosity of the fluid, weight of the particle ......
0answers
71 views

### Can a projectile moving at supersonic velocities leave a silhouette in whatever it hits?

I was recently reading this, and Floris's answer confirmed my knowledge that the information of an collision travels at the speed of sound. While I was thinking about that, my mind wandered and I ...
0answers
95 views

### Physical Interpretation of four velocity in GR

I'm confused about the physical interpretation of the four-velocity $U^\mu=\frac{dx^\mu}{d\tau}$ in General Relativity. I know that it is a tangent vector to a particle's "worldline", but what does ...
0answers
95 views

### Relativity addition and signs

I have just covered a very brief module on special relativity as a part of my physics course. I have also done some extra reading mostly; Morrin's Classical Mechanics. While I found the book really ...
0answers
109 views

### How to formally write down the Boltzmann equation?

Can someone write down the Boltzmann equation, not neglecting any of the variables of the involved functions and integrals? Specifically, how to concisely capture the "primed" variables in a sensible ...
0answers
45 views

### How do we generalize limitations on the propagation speed of sinusoidal waves to limitations for transmitting any kind of information?

Our calculations on EM waves basically deal with harmonic waves and through such calculations and relations, we derive some relations and limitations for wave like phenomena. Of these relations are ...
0answers
238 views

### Saturn V specific impulse issue in velocity modelling with Tsiolkovsky's equation against actual values?

I've been trying to model the Saturn V's velocity using Tsiolkovsky's ideal rocket equation, and in the process, I think I may have made a mistake with regards to the specific impulse? I've come up ...
0answers
90 views

### What do the components of light velocity look like in polar coordinates?

The Schwarzschild solution makes use of polar coordinates, and I'm wondering how the different components of velocity of light change with the position. Might I get some examples of light velocity ...
0answers
193 views

### Is there any place you can safely skydive without a parachute?

While trying to explain to someone how a kitten walked away from a fall from a skyscraper I got to wondering if there's any place a human could do that and I find myself out of my depth. The only ...
0answers
213 views

### 2D Car Physics including Throttle

For a simulation for testing on automatic cruise control, I came across the equation: $$v_{n+1} = (1 - k_1 / m) v_n + (1 - k_b) \begin{pmatrix} T_n \\ θ_n \\ \end{pmatrix}$$ where: $T$ = ...
0answers
57 views

0answers
251 views

### What is the physical explanation for the phase relationship between acoustic pressure and particle velocity in plane and spherical waves?

I've been looking around for a decent physical explanation of the differences in the phase relationships between acoustic pressure and particle velocity in different types of waves. Mathematical ...
0answers
151 views

### Bernoulli's equation

So there's a pipe filled with water that has 4 other pipes with same radii connected to it. The question is to arrange heights from the smallest to the biggest level in it. $A_1$ and $A_2$ are ...
0answers
62 views

### Two impulses on body

Say I have a physics simulation with a single body with three degrees of freedom (two axis and rotation). I have two impulses of equal magnitude in opposite directions. When applying these impulses in ...
0answers
517 views

### What direction a flag on an object moving in the wind shows?

"The flag of a ship that is moving northward with 10 km/h, points exactly southwestward. The windsock at the lighthouse points under 30 relative to the western direction southward. Calculate the ...
0answers
107 views

### Physics behind 2 different wall kicks

I'm looking at a situation where a sprinter starts at some distance x from a wall. The goal is to sprint to the wall, hit it, and get back to the start as quickly as possible. There are two ways ...
0answers
32 views

### Relating Initial velocity and acceleration to distance traveled up a ramp

This is the situation: I am conducting research on the ability of fin-fish to scale short wetted ramps for use alongside sea-lamprey barriers to allow non-target species to pass these barriers. We ...
0answers
13 views

### Velocity in harmonic motion - Why are these angles congruent?

I learned about harmonic motion and I found the derivation of the formulas: And so, the velocity in harmonic motion is the projection of the velocity in angular motion. The only thing that is not ...
0answers
33 views

### How to derive velocity, distance from a changing acceleration?

I'm making a electronic device that is out of the scope of this site, but essentially it gives me acceleration readings every X microseconds. Given these samples of acceleration, how can I find out ...
0answers
30 views

### For two electron that moving parallel,can we using this equation for Electric Field and Magnetic Field?

i suppose we have two electron and they are moving parallel,please see picture: my question is can we use this this equation for it? Griffiths' Introduction to electrodynamics): \vec E(\vec r,t)=\...
0answers
109 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 ...
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 ...
0answers
13 views

0answers
25 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 ...
0answers
38 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 ...
0answers
31 views

### Real and relative velocity formula

What i need is a thing more complicated than the usual relative velocity formula. Imagine a radar. You are at the center, moving at some angle, but lets make it clear, you are always at the center. ...
0answers
53 views

### Elastic Collision of Infinitely Large Body and an Infinitely Small Body

So I guess this is a somewhat conceptual question. There are two bodies, one with a mass $m$ that is so light it is massless and at rest so $v_{_i1} = 0$ And the other with mass $M$ that is almost ...
0answers
20 views

### Representing variable velocity in cellular automata

I've read through some of the more non-physicist accessible material on cellular automaton, touching on digital physics etc and I am somewhat confused about methods to reason with variable velocity in ...
0answers
46 views

### What's the formula to determine how fast a magnet can travel and still hold objects in it's magnetic field?

If an object (an iron ball) is locked (suspended) in the magnetic field being produced by a magnetic bar, what is the maximum velocity at which the bar can be moved before the iron ball is disturbed ...
0answers
25 views

### Help with a problem in magnetism, kinetic energy

I couldn't fully understand how the author solved the problem c). Here's what was done: At first I thought he changed $v$ for $\sqrt{\frac{2K}{m}}$ in the equation $r=\frac{mv}{|q|B}$, but instead ...
0answers
72 views

### Position from acceleration, or acceleration from position, to track an object moving the speed of sound

I'm working on a project that involves tracing the motion of a fast-moving object (approx the speed of sound) through a fairly defined trajectory. Would it be more accurate to measure the position of ...
0answers
27 views

### 4-velocity in an accelerated frame

I am trying to check some calculations of the displacement tensor from a paper that has been given to me by my advisor. And it seems I am stuck on the form of the 4-velocity in an accelerated frame. ...
0answers
17 views

### Issues determining velocity in a totally elastic collision

A block of mass $M_1$ is attached by string to a support. The block is raised to a height and released. It then strikes a block of mass $M_2$ on a frictionless surface. Find the velocity of block $M_2$...
0answers
119 views

### Symmetry considerations in Plane Poiseuille Flow

I'm taking a first course on fluid dynamics, and I have this (sort of) conceptual question that's been nagging me for a moment now. I can completely follow the mathematics behind the derivation of the ...
0answers
63 views

### Kinetic Energy and reference frame

Two space ships A and B moving through space in the same direction. Space ship A moves 2m/s faster than B, its weight is 1kg and it has a 2 Watt engine. It is accelerating with full power for one ...
0answers
46 views

### Bezier curve and deceleration

I have a question regarding calculation of a bezier curve. I'm programming an app where in there's continuous straight line motion of a vehicle at a constant speed. (Let's call it 'u'). When the user ...
0answers
67 views

### Centripetal acceleration for a polyline

This question is also posted on the Mathematics forum. I am not physicist, therefore sorry if my question is a bit primitive. Given a polyline (x and y coordinates) in Cartesian coordinate system, ...
0answers
743 views

### How to calculate the centerline velocity inside a pipe?

Well, I was reading about fluid-solid/structure interaction models for make a simulation in COMSOL, and in few papers about it [1] I find an expression about the centerline velocity. I understand the ...