The description of the movement of bodies by their position, velocity, acceleration (and possibly higher time derivatives, such as, jerk) without concern for the underlying dynamics/forces/causes.

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2answers
196 views

Why does a plane look like it's slower than a car?

Recently, I was in a car and noticed a plane in the sky. What was interesting was that the plane seemed to go slower than my car because I passed the plane. Is there a physics reason to this?
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2answers
71 views

Jumping insect acceleration question [closed]

From my book, verbatim: The froghopper, Philaenus spumarius is supposedly the best jumper in the animal kingdom. To start a jump, this insect can accerate at $4.00 km/s^2$ over a distance of $2.00 ...
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1answer
47 views

How to find velocity at the end of $n$th second [closed]

A body travels 10m in first three seconds and 15m in next four seconds. What is the velocity at the end of 8th second? And this is not a homework question. Just I Found it in a book... Ok If the ...
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2answers
48 views

Can we say that the instantaneous velocity of an object is the displacement in zero time?

Can we say that the instantaneous velocity of an object is the displacement in zero time? In the image above the instantaneous velocity of the object as change in time gets closer and closer to ...
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1answer
153 views

Shouldn't motion be represented as a Taylor series rather than a finite sum of functions or a polynomial? [closed]

Since the change in velocity of an object at rest prior to time $t_{0}$ implies a change in acceleration — that is, let's postulate, $ \mathbb{P} $, the object would have remained still, so there was ...
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2answers
45 views

Rate of deceleration for an average speed [closed]

I'm trying to figure out how to answer this problem: A car is driving at 11 m/s, when it begins to brake. Over the next 25 meters, it averages 6 m/s. At what rate does the car decelerate? Assume a ...
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1answer
143 views

What happens to kinetic energy of an object when i stop its motion? [duplicate]

Assume an object is moving and it is stopped at a point . Now kinetic energy will transform into some other energy . what can be those energies and on which cases these will happen respectively ? ...
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0answers
10 views

Resources for Kinematics [duplicate]

I find that I am having difficulty solving problems dealing with kinematics such as a ball being thrown and the air and being asked to find initial velocity as well as time. My main issue is the fact ...
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2answers
83 views

Photon energies after neutral pion decay

I am trying to find the photon energies of the decay $\pi_0 \rightarrow \gamma\gamma$ and their dependence on the pion energy $E_{\pi}$, its initial velocity $\beta$ and the scattering angle between ...
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0answers
41 views

Time Given Distance and Velocity Vectors [closed]

I recently came across a problem that gives velocity and two positions (which I solved for distance) in vector notations (). My question is, given the vectors for velocity and distance, how do I solve ...
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0answers
48 views

For a bob on a pendulum following simple harmonic motion, what causes the bob to accelerate towards the centre of equilibrium?

*The position of equilibrium being the position of the bob when the string is taut and vertically downwards. When I draw a simple diagram, I see that the tension of the string, which always acts ...
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2answers
42 views

What are the major differences in group-skydiving as opposed to “single” skydiving?

Surface area/the cross-sectional area is greatly increased, so my thinking is it should decrease terminal velocity as well as a couple of other factors. But mass changes too (since there would be more ...
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1answer
49 views

Kinematics equations of motion find x position in 2D from height

I have a question and I thought of 2 possible ways to answer it however the resulting answers are different which means I must be doing something wrong in my calculations. All the below happens 2 ...
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0answers
40 views

Searching for acceleration to minimalize path or time

I am thinking about motion of one point starting from $(0,0)$ and with velocity $\mathbf{v}(0)$. What is the acceleration $\mathbf{a}(t)$ with condition $|\mathbf{a}(t)|<M$ that minimalize ...
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1answer
43 views

Work done: kinetic energy or area under F-ds curve?

Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE. Suppose a variable force is ...
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2answers
60 views

Solving distance with acceleration and velocity given and getting two different answers using two different equations [closed]

Frictional forces from brake pads are responsible for stopping an automobile. A car is moving at $35.0 \:\mathrm{m/s}$. If the car's brakes are capable of generating a deceleration rate of $6.00 ...
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2answers
101 views

Is it possible for a moving body to have no kinetic energy? If yes, then how? [closed]

An object which is moving relative to your coordinate system has kinetic energy in that coordinate system; it does not have kinetic energy in a coordinate system which is stationary relative to the ...
2
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1answer
101 views

Predicting balls's movement in well due to fluid flow

I am a total newbie in fluid dynamics. In one of my experiments/open project, my experiment setup is as below: a small ball sits in a circular well (has mass density a bit heavier than water), with ...
2
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0answers
69 views

Heads, Tails… Edge?

No Nobel prizes at stake, but just an idle thought and an idle question. How could one calculate the probability of a flipped coin landing stable on its edge, instead of heads or tails? I assume ...
2
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1answer
109 views

From acceleration to displacement

Hi I am a major in Computer science and this question should be really easy for all the physics geniuses here: I have a set of data points from an accelerometer on a moving object that basically ...
2
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1answer
65 views

Curvature of a particle move

I'm simulating a particle movement following a normal distribution. How this is done: My particle has a constant speed v and every step the particle move, I ...
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1answer
58 views

Projectile at an angle. Finding the angle using conservation of energy [closed]

Ball is thrown at an angle α and at the highest point it's potential and kinetic energy are the same. Find the angle. Use the law of energy conservation. What the professor wanted $mV^2/2 = 2* ...
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1answer
107 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newtons third law and Momentum conservation. Here is what I have tried. Lets take $m_1$ (the ball) hits $m_2$ (the man). ...
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8answers
523 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 ...
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1answer
74 views

Prove the relation between relative velocity ,momentum and energy

In Chapter 8 of F.Mandl's book Quantum field theory, during the derivation of the differential cross section, the following relation is used: $$E_1E_2v_{rel}=\sqrt{(p_1p_2)^2-m_1^2m_2^2} \,\, ,$$ ...
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2answers
88 views

Kinetic Theory of Gases: Why do gas molecules have translational motion?

The title pretty much asks the question. I was reminded of the Kinetic Theory of Gases recently and I am puzzled as to why gas molecules would have any translational motion. Is it because collisions ...
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1answer
29 views

cross over to another object that has same height with our last position, is that really possible?

I have got confused with this. Well..In that picture, lets say the height is 8m, and the car moves and going to cross over to another object that has the same height with its last position..my ...
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0answers
35 views

Describing the motion of a point-mass [closed]

Consider a point-mass moving around a fixed point on a circle with radius $r$ with constant angular velocity $\omega$. At a certain moment of time, the connection is removed, and the point-mass flies ...
2
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1answer
57 views

Different results for displacement using different Kinematics equations

We drop an object from a height. It displaces a distance $L$ in the $\vec{y}$ direction. So: $$ L = \frac{1}{2}at^2 $$ Or: $$ v^2-v_0^2 = 2aL \rightarrow L = \frac{v^2}{2a}$$ How much would the ...
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1answer
67 views

How to calculate the horizon line of a satellite?

I need an equation to calculate a list of Earth-centered, Earth-fixed (ECEF) XYZ coordinates on the earth that represent the visibility limit of satellite given its ECEF XYZ coordinates. For any ...
0
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1answer
67 views

Is velocity always tangential to trajectory?

So I was doing an exercise and they find find the angle between the tangential of trajectory and the vertical I was stuck but then I read in a site that the velocity is ALWAYS tangential to the ...
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0answers
40 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
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0answers
17 views

temperature and velocity exchange

So there is a relation between total temperature and velocity of a fluid. In an adiabatic flow what determines how much one property (velocity or temperature will change)? I know the equation. But ...
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2answers
55 views

Adding rotations onto a vector

I have a vector with spherical co-ordinates $(r_1,\theta_1,\phi_1)$, then I want this vector to be rotated by $\theta_2$ $\phi_2$ spherical angles but I cannot figure out how. I have tried using the ...
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3answers
41 views

Find time-parametrization given path and speed of a particle

Consider a particle in two dimensions with position vector $r(t)=<x(t),y(t)>$ and the shape of the path is described by a function $y(t)=f(x(t))$ (Thus $r(t)$ is a parametrization of $f$ with ...
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2answers
33 views

About using screw in air compression and air Engine [closed]

I want to use screw to build compressed air engine, as following image As I designed, this screw rotate in a tube My Question is: How successful this idea? Note: If this question not related to ...
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1answer
26 views

Kinematics problem regarding motion of a particle [closed]

A particle of mass m moves on the $x$-axis as follows: it starts from rest at $t = 0$ from the point $x = 0$, and comes to rest at $t = 1$ at the point $x = 1$. No other information is available about ...
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0answers
24 views

How does momentum effect velocity? [duplicate]

I'm in AP physics and we haven't even covered this yet so sorry if my question seems strange... I know $p = m v$, However right now I am writing a 2D physics engine and I am having some trouble with ...
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1answer
33 views

How do you measure the acceleration of two objects with different masses? [closed]

I would like to know how to measure the acceleration of two objects with different masses...(and the formula that's used.) For instance a steel ball that, say...weighs 67g and a wooden ball that ...
9
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1answer
150 views

Relating momentum fraction to rapidity in a high-energy collision

It's a well-known result in particle physics that in an underlying interaction like this: assuming $p_0^-,p_{0\perp},m_0\ll p_0^+$, $m_1$ and $m_2$ are small, but $p_{1\perp}$ and $p_{2\perp}$ are ...
1
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1answer
26 views

Computing the Initial Velocity of an orbiting body

I'm working on a simulation program that replicates the movement of planets around a large celestial body (the sun). This is a three dimensional simulation that uses vectors. At present, I'm ...
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3answers
69 views

How to account for inertia in kinematics?

Alright, I'm only in AP Physics and I asked my teacher and he couldn't help me... I'm making a 2D physics engine and I'm having problems when it comes to gravity between objects and I think its ...
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1answer
69 views

What is the point of this type of graph? (Projectile) [closed]

What is the point of graphing vs range, during kinematic motion?
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3answers
156 views

Problem in deducing the equations of motion using indefinite integral

As we know, antiderivative or indefinite integral is the function the derivative of which gives the actual function. Let $F(x)$ be the derivative of $f(x)$ ie. the instantaneous rate of change of ...
0
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1answer
44 views

What is the movement of the material point? [closed]

The parametric formulas for movement of a material point are: $x(t) = A \sin (kt)$ $y(t) = B(1 - \sin(kt))$ Describe the movement of the MP. That is the entire question and I can't find a ...
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0answers
35 views

Why we don't integrate intital velocity in body cast equation?

On this site I've found a formula for calculating the $x, y$ coordinates for a body throwed by an angle to a horizon. It looks like this: $$x(t) = V_0 t \cos(\alpha); $$ $$y(t) = V_0 t ...
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4answers
118 views

How is acceleration measured if there is change only in the direction of velocity & not magnitude?

The formal definition of acceleration is It is the measure of how fast the velocity changes with respect to time. Now, when the magnitude of velocity changes, acceleration $$\vec{a} = \frac{d ...
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0answers
20 views

Change velocity formula from a function of displacement to a function of time [closed]

I have this problem from my dynamics book and I can't figure out how to solve it. I've played around with all the formulas and asked a few friends who did the course in the previous years but I can't ...
2
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2answers
297 views

Velocity of car down an Inclined Plane

I was learning to make a car game and came across this situation where my car is on an inclined plane. It's initial velocity is 0. Now, the problem is that my memory serves me this formula to ...
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1answer
79 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 ...