The time rate of change of the position of an object

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24 views

How do I find the co-ordinates and speed of this particle on the x-y plane? [on hold]

I got this question from an old physics exam paper. I'm trying to use the kinematics equations to solve this question but the x and y co-ordinates keep confusing me. Here's the question: A particle ...
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4answers
66 views

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

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 ...
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2answers
44 views

is photon direction affected by source velocity? [on hold]

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
41 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): ...
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1answer
55 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 ...
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1answer
38 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 ...
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0answers
12 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 ...
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2answers
31 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?
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0answers
16 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
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1answer
32 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 ...
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1answer
30 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 ...
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4answers
84 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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1answer
27 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 ...
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0answers
187 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 ...
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1answer
50 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 ...
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1answer
49 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
79 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
44 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 ...
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0answers
19 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 ...
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1answer
61 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 ...
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1answer
35 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 ...
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1answer
31 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 ...
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votes
3answers
69 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. ...
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1answer
46 views

Empty space and velocity

If there was a universe without anything in it except you in a space rocket how you would you know what your velocity if you kept the engine on?
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1answer
53 views

Objective velocity (Relativity theory) [closed]

Suppose that I have a velocity of (approximately) $c$. Then I decelerate with $c$ per hour for exactly one hour. Then I would know that I would be standing still in the end, because the decelleration ...
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0answers
26 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 ...
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1answer
29 views

Finding acceleration using components method

The problem I am working on gives me an initial velocity of 2[E15N] m/s and a final velocity of 4[E35N] m/s after 30s. I need to find acceleration so I create a right angle triange for both of these ...
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1answer
36 views

Having trouble understanding projectile motion [closed]

So, I learned about projectile motion in class a fe days ago, and am having trouble understanding. I main problem is seeing how velocity works in projectile motion. For example, why is the velocity in ...
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0answers
25 views

How can a net force of 0 still lead to movement and how is movement possible with interaction pairs? [duplicate]

So I always thought of movement as interaction pairs. For example, I thought that a rocket moves by applying a force of hot exhaust gases, which then apply a reaction force back on the rocket ...
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1answer
46 views

Difference between escape velocity and speed [duplicate]

What is the difference between escape velocity and escape speed , is their any error if we use them interchangeably?
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1answer
62 views

Question about acceleration & deceleration in real world?

have searched the net and am not satisfied with any answer I have found to calculate the following:- Here is an example just for reference. Suppose I can accelerate my car from 0-100km/h in 10s. That ...
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1answer
37 views

At what velocity was this car traveling? [closed]

Throughout schooling we are given problems in which we are to solve for velocity, force, mass, etc. I have a real life situation in which I would love to solve these exact things. Please consider: Car ...
5
votes
5answers
313 views

Why is rapidity additive?

With the rapidity $\phi$ defined so that $\frac{v}{c}=\tanh{\phi}$, say you have 3 parallel moving reference frames $S$, $S'$ and $S''$ with a constant but different velocity/rapidity. If the ...
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2answers
39 views

motion with constant acceleration question! [closed]

Consider a motorboat maneuvering on the surface of a lake, Is it possible for the boat to have accelerated motion in the x axis and unaccelerated motion in y direction?
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1answer
43 views

Velocity of a liquid jet, coming out of a container

Think of a container which has a hole beneath it. And we have filled the container in height $h$ with a liquid of density $\rho$ and cross section of the hole $a$. (look at the pic) Then what is the ...
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0answers
24 views

How does a bikerider turn by leaning on one side? [duplicate]

I am trying to understand the following image: Could someone please help me understnding it. What I understood so far: Your angular velocity mutyplied by the impulse gives you the impulsemoment. By ...
2
votes
1answer
40 views

Why is the potential independent of the generalized velocity?

In Goldstein, Classical Mechanics, Chap. 1.4 we derive Lagrange's equations from D'Alembert's Principle. My question is regarding the last part of the derivation, specifically the part where he ...
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2answers
49 views

Calculate velocity with acceleration caused by drag

Maybe someone can help me with calculating the velocity of a sphere falling down. Initial: Acceleration is $10 ~\rm \mathrm{m/s^2}$. Timestep is $1 ~\rm s$. Approximation of drag = ...
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1answer
151 views

Jumping from a moving train

If you were to jump from a moving train at 20 km/h, would it be better to run in the direction of movement before jumping to maintain inertia or in the opposite direction of the train ?
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0answers
27 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. ...
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2answers
106 views

Velocity time graph for a ball thrown vertically upwards and falling back down to be caught again by a person

I am currently studying AS level physics and having some difficulty understanding the shape of a velocity time graph that represents the motion of a ball being thrown upwards and falling back down to ...
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0answers
24 views

Retardation on a Conducting Object in a Magnetic Field [closed]

I cannot solve this question and I need help to understand the physics. The picture below says it all. What is the retardation (negative acceleration) on the conducting object with a mass of 2.5 kg's ...
0
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1answer
46 views

Velocity of water from a certain depth

I was curious to know does water come out of a certain depth when there is a difference in pressure, and also if it does come out of a certain depth, at what velocity does it travel at? So, ...
0
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0answers
17 views

Do we have the potential technology to harness the energy the Earth is constantly giving us? [duplicate]

Messing around with fun physics, and it got me thinking. I probably am not the only or the first one to think of it. I am wondering what more experienced physicists on this site can contribute to this ...
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0answers
38 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 ...
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0answers
12 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 ...
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1answer
92 views

If an object's acceleration is zero, can its velocity be non zero?

Question: If an object's acceleration is zero, can it's velocity be non-zero? Explain by giving an example. My Attempt: This doesn't make any sense at all. Via my teacher's solution ...
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0answers
12 views

Calculate distance with variable acceleration [duplicate]

I know the time and I know the force that acts horizontally on a particle. The problem is that the force is F=k(D-V), where k and D are constants. So at the beginning where the particle has zero ...
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0answers
37 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 ...
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1answer
56 views

Tachyons and Lorentz velocity transformation

In general, is it possible to apply the Lorentz velocity transformation to a tachyon? I have tried to do so but the results seemed very illogical. Here's my attempt: suppose an evil spaceship named ...