The time rate of change of the position of an object

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2answers
43 views

How can I calculate the change in velocity? [closed]

"A runner runs at 4 m/s on a circular track constantly. A and B are opposite points on the track, so A is the starting point and B is halfway around the track. Calculate his change in velocity from A ...
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1answer
23 views

Equation for Turning Projectile

I'm trying to cook up an equation that will give me position for a projectile which operates in the Newtonian Domain. So a the fall equation is: $$\mathbf{p_t} = \frac{\mathbf gt^2}{2} + ...
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1answer
79 views

How to determine when to decelerate to reach a destination at 0 velocity?

(Sorry, not sure whether this belongs here on the Physics StackExchange or the Math StackExchange.) I'm creating a computer game in which there is a computer-controlled car that needs to travel along ...
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0answers
24 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 ...
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1answer
196 views

Understanding rotational motion on a rough surface

I am having trouble gaining an intuitive understanding of rotational motion for an object rolling on rough surface, and I have a few questions regarding it. Let's say that there's a cylinder that ...
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1answer
18 views

Need to find module of magnetic field

I have a post-lab problem During the experiments I have a U magnet on a scale. Inside the U magnet there is a conductor with a steady current. The conductor is made so that the magnetic field is ...
0
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4answers
340 views

Is $\left|\frac{d\vec{r}}{dt}\right| = \frac{d|\vec{r}|}{dt}\;$?

Is magnitude of instantaneous velocity same as instantaneous speed? More specifically, is $$\left|\frac{d\vec{r}}{dt}\right| = \frac{d|\vec{r}|}{dt}\; $$ Also Is it wrong to say that ...
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5answers
2k views

Time dilation at zero velocity (and zero gravity)

From what I've learned, the more an object travels closer and closer to the speed of light, the more time will slow down for that object.. at least from an outside perspective.. It was shown that ...
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1answer
40 views

Calculating position of a particle at time $t$ in a gravitational field

I'm working on a piece of code that is supposed to visualize a particle bouncing up and down from the ground (somehow magically we can give it velocity upwards when it is on the ground). I figured ...
0
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2answers
78 views

Obtaining Velocity from Acceleration

I'm following a research paper (PDF via RG), part of which is about using the accelerometer of a smartphone to assist the user's positioning via WLAN. Accelerometer is used to determine if the user ...
1
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2answers
172 views

Terminal Velocity of 100lb Hail [closed]

In the Apocalypse there is meant to be hail weighing 100 pounds or 45 kg. What would the terminal velocity be, assuming the hailstones are perfect spheres of solid ice? Also, is there a way to guess ...
1
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1answer
78 views

Relativity: easy spaceship scenario. easy questions [duplicate]

Your spaceship is traveling at 1/2*c and you approach Bob's spaceship going -1/2*c in the opposite direction. Relative to you, Bob is going the speed of light, and of course he has a giant ticking ...
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0answers
51 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 ...
0
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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. ...
0
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2answers
48 views

Where does the energy required to speed the object in this question come from if the object actually slows down from another perspective?

I was thinking about mechanics and energy and stumped myself with this scenario I made up: Suppose you are in a room and you are motionless. In the same room, a 1 Kg ball is moving to your right with ...
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2answers
38 views

Acceleration vs. Velocity

Since acceleration is a change in velocity or a change in direction how can in reality velocity exist since a straight line does not exist except in Euclidean geometry? Any movement from one point to ...
1
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1answer
44 views

Example of physical phenomenon with zero velocity at some point that does not correspond to an extremum [closed]

For many students (at least mine), the vanishing of the derivative $f$ at some point means that the function is maximal at that point. The cubic function $f(x)=x^3$ shows this is false. Students ...
0
votes
1answer
77 views

How do I measure speed accurately without any turning wheels?

Consider a pod (about 50 ft long and 15 square feet wide) that levitates using air pressure that shoots through the bottom and travels through a tube that's at low air pressure (about 100 Pa). It ...
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0answers
25 views

How to compute the speed of a cosmic ray from its energy? [duplicate]

How can you compute the speed of a cosmic ray from its type and measured energy? For example, if a cosmic ray were said to be a proton of 10 GeV, how would you compute the velocity of that cosmic ...
0
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2answers
64 views

Why wasn't the theory that light's velocity depended on its source very popular?

Before special relativity, it was believed that light having a specific velocity meant it had to travel through something. My question is, why wasn't the idea that light depended on its source very ...
3
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9answers
905 views

Can velocity be an undefined quantity?

We have the image below displaying the uniform velocity by time-distance graph. At every point velocity is constant but what if distance and time both become zero as at origin in the graph is? The ...
0
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0answers
40 views

Speed of Light with trains [duplicate]

Suppose that there is a train (train1) going at 100 km/h. The train is infinitely long. Suppose that there is an other train inside train1 (train2), which has a speed of 100 km/h also. So for a ...
2
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1answer
93 views

How far will the bullet travel before falling back to earth? [closed]

First, the question: A particular high performance rifle cartridge can be fired with a muzzle velocity of 1200 meters per second. The rifle is pointed straight up. Assuming there is no air ...
2
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2answers
2k views

I don't understand the idea of perpendicular vectors being independent of each other?

So problem 71-75 is about vectors. The problem says: A river has a current flowing with a velocity of 2.0 meters per second due east. A boat is 75 meters from the north riverbank. It travels at ...
0
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1answer
96 views

Questions about the velocity of the center of gravity

I have a physics test coming up in a couple of days and I really need to have some things explained to me. It is about something that I think is called in english "the velocity of the center of ...
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2answers
176 views

stopping a rotating mass to achieve linear velocity

So I've been thinking about space, and I had this idea. I haven't found any prior art online for it, and from my limited understanding it seems like a viable idea. So I guess my question is, what am I ...
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1answer
44 views

Calculate the distance of a falling object and terminal speed [closed]

I have a homework problem that I would like to verify that I am doing it correctly. If anyone could help me see where I'm going wrong with the steps, I would really appreciate it. (a) Consider a ...
0
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1answer
68 views

For a particle moving in a circle,can $a_t\neq 0$ and $a_r= 0$? [duplicate]

I know for a fact that if a particle is moving in a circle such that the value of radial acceleration is non-zero and the value of tangential acceleration is zero ,then it can be classified as ...
0
votes
1answer
63 views

Differential equation for velocity regarded as a function of distance [closed]

Given a differential equation for velocity, $dv/dt + v = 1$, as well as its solution, is it possible to derive a differential equation for velocity with respect to distance? I found a solution to the ...
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2answers
271 views

How to find the height at which a projectile is launched from an angle? [closed]

I need guidance with the following question: A boat is $50.0m$ from the base of a cliff, fleeing at $5.00m/s$. A gun mounted on the edge of the cliff fires a shell at $40.0m/s$ and hits the boat ...
0
votes
1answer
41 views

magnetic field strength paradox-where is my error in reasoning?

Under the assumption that I understood the following circumstances correct: Magnetism occurs when a charged particle moves with a certain velocity through space. Faster velocity equals a stronger ...
2
votes
2answers
102 views

What is meant by the velocity of a star?

I recently read somewhere that among other things like size, radius, distance from earth, luminosity, age, etc of a star, velocity was another variable. What is exactly meant by the velocity of a ...
1
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1answer
38 views

Speed of different inclined plane [closed]

Assume friction-less, an object was release from the top, what is its speed at the lower end of the slope? I tried $v= \sqrt {2*9.0m/s^2*5m}$, but I doubt if it's a correct answer, any help?
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6answers
722 views

What is the acceleration at the top most point of a ball’s journey vertically upward?

When i shoot a ball vertically upward, it’s velocity is decreasing. So there is acceleration. -9.8m/s^2. I’ve read that at the top most point, the acceleration is STILL 9.8 m/s^2 where v=0 . The ...
0
votes
3answers
215 views

Deceleration of a bullet [closed]

Taking into account gravity, air resistance, and wind velocity and direction. (And also temperature if it's actually relevant.) I know the muzzle velocity, the total distance the bullet traveled, its ...
6
votes
3answers
881 views

Does an ion thrust engine consume more energy as it speeds up?

This question goes to a very basic non-understanding of mine that I have had in the back of my mind for ages - I just read the following here: ion thrusters are capable of propelling a spacecraft ...
0
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2answers
89 views

Velocity of photon when changing direction [duplicate]

We know the speed of a photon is constant. Yet when any other object changes direction, its velocity must go to zero. Thus, my question is how does a photon avoid this? I assume that to change ...
0
votes
2answers
93 views

Calculating Acceleration

I'm having problems calculating acceleration for the following variables. I would have thought it would be extremely straight forward, except I am getting two different answers and do not know which ...
0
votes
1answer
59 views

Why the point right below the center of a rolling ball on the ball has zero instantaneous velocity [duplicate]

Suppose there is a snooker ball rolling on a table. The velocity of the center of the ball is Rω and its direction is horizontally right. I don't understand why the point right below the center on the ...
0
votes
1answer
44 views

What is the change in velocity? [closed]

A boat moves with a velocity of 22 m/s directly west. Later, the boat is found to have a velocity of 12 m/s at 45° S of W. What is the change of velocity? I want to do this vector wise. I know that ...
0
votes
3answers
76 views

Finding velocity from distance and gravity

Basically, I have a problem that asks: An object is launched to a height of 2 miles, what was it's initial speed and time. Now normally something like this would be fairly basic. The problem ...
0
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4answers
219 views

Meaning of fourth component of velocity four vector

Can any one help me to understand what the fourth component of velocity four vector mean physically?
8
votes
5answers
2k views

How to brake 'beautifully'?

Sometimes when I'm driving my car, I play a "game" against myself in which I try to minimize the deceleration felt by passengers (including myself) while still braking in a reasonable short space. I ...
0
votes
2answers
126 views

Kinematics with acceleration as a function of velocity

Say there is a particle moving at $50~\text{m/s}$ and modeled with a function of acceleration such that: $$a = - 0.5v$$ (this is derived from a force as a function of velocity) $$F = 50v = ...
-1
votes
2answers
72 views

1D Kinematics problem [closed]

The position of a particle in meters moving along the x-axis is given by: $x = 3(t − 2)^2 − 12$ for $0 \le t \le 15$ How can I find the velocity of the particle when it is passing through the point ...
1
vote
1answer
164 views

How does the angle between two objects change relative velocity?

I apologize in advance if my question isn't clear. If two objects start from the same position, but leave in opposite directions--say $40^0$ west of north, and $50^0$ east of north--how would an ...
-1
votes
1answer
119 views

Mass of a particle ( relativity)

A hypothetical atom has a rest mass of $15.000000136\,\mathrm{u}$. Overtime it undergoes a spontaneous breakdown into two masses of $7.000000229\,\mathrm{u}$ and $6.902727019\,\mathrm{u}$ ...
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2answers
328 views

Finding acceleration and distance when velocity given

I am trying to do the following question for practice (it is an interview question), and I don't know if my methods and answer are correct. Given a velocity $v=2+3t^2$, find acceleration after 3 ...
-3
votes
1answer
34 views

Calculating Changes in Velocity [closed]

When $+6.0$ m$\cdot$s$^{-1}$ becomes $+15$ m$\cdot$s$^{-1}$ is it said to have a change in velocity of $9$ m$\cdot$s$^{-1}$. If so, when a direct velocity such as $+6.0$ m$\cdot$s$^{-1}$ changes to ...
0
votes
3answers
153 views

Our speed and direction by comparing the speed of light?

If the speed of light is constant no matter the speed of the source, shouldn't we be able to know the direction and exact speed we are going relative to the absolute 0 in speed? If a photon is sent in ...