Questions tagged [kinematics]

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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Question about the value of angular displacement [closed]

Can angular displacement be greater than $2\pi$ radians? Is $5760$ radians correct here or should we do something like this: $\frac{5760}{2\pi} = 916.732472209$ $0.732472209 \cdot 2\pi = 4....
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What does this vector represent?

Let $p$ is the position vector from the origin of frame {s} (i.e. inertial frame) to the origin of the body frame {b}. Take a look at the following picture, the vectors $\omega_b,v_b$ represent the ...
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Does Newtonian mechanics work in polar coordinates?

Our teacher suggested that Newtonian Mechanics only applies in cartesian coordinates. Is this true? He gave this example. Suppose there a train moving with constant velocity $\vec{v}=v_0\hat{x}$, with ...
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What is the minimum speed at which the proton has to move for antiproton production? [duplicate]

In a collision between 2 protons. Do each of them have to move at 1c, 0.5c.. ? The lower the speed, the less likely the production of the antiproton?
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2 votes
1 answer
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At what speed do newly created protons move after a proton-proton collision?

I read that when 2 protons travelling at near the speed of light collide with each other, they create 3 protons and 1 antiproton. At what approx. speed those 3 new protons usually move once they are ...
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Which equation is more suitable when a man lifts his leg in fluid (such as snow, sand or mud), Drag equation or Stokes's law, or other equation? [closed]

When a person lifts his leg in fluid (such as snow, sand or mud), what kind of resistance/viscous force will his leg encounter in the vertical direction, which equation is more suitable? Drag equation ...
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Uncertainty propagation time difference

So for an experiment we gathered time data. It a rolling object, where t2 and t1 are measurements of one whole roll of circumference. We estimated time uncertainty at 5 ms. ​ So then estimation of ...
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4 answers
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Why are areas of graph taken with respect to $t$-axis in velocity time graphs?

If the following graph is given then, why is the displacement equal to the area of the shaded triangle above the axis minus the are of the shaded triangle below the $t$ axis. Why can it not be area of ...
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Classical mechanics / system of particles

Three particle A, B and C situated at the vertices of an equilateral triangle starts moving simultaneously at a constant speed $v$ in the direction of adjacent particle, which falls ahead in the anti-...
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3 answers
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When a car turns does any part of it cross to the other path?

I always believe when a car is making turn, some parts of it (either the front corner or the back overhang) will go more into my path momentarily, is this true? Does it make a difference if the car is ...
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Momentum and Kinetic energy from a decay of single particle at rest into 2 particles

How can I find the kinectic energy $KE_n = E_n - m_nc^2$ and the momentum $ p_n = \frac{1}{c}\sqrt{E_n^2 - m_n^2c^4}$ From $E_n = (\frac{m_{\lambda}^2 + m_n^2 - m_p^2}{2m{_\lambda}})c^2$, which result ...
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1 answer
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A projectile with huge initial speed

in a projectile, if the value of initial speed is very large, 2000 m/sec for example, and the shooting angle is not equal to 0 degrees why would the rules of the maximal height and range (maximal ...
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Under which conditions the collision front between two bodies stops?

Imagine body 1 and body 2. Each body is made up of $n$ and $m$ deformable elements, respectively, all with elastoplastic behaviour. Body 1 and body 2 are aligned vertically and body 1 falls from an ...
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What is the physical explanation of why a $45°$ projectile angle gives the absolute maximum range? [closed]

Assuming, start and end positions are at the same height and there is no air drag. How gravity's role plays out during flight of projectile?
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Initial speed of a released object from a moving object

For example, if a helicopter is moving upwards in constant velocity of 20 m/s and at some height an object is released from the helicopter, why does the object has an initial velocity of 20 m/s and ...
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6 votes
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Vector Addition of velocity [closed]

In the arrangement shown in figure, the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. The mass M moves upwards with what speed? I tried to ...
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Different equation is given for "position"

$$s=ut+\frac{1}{2}at^2$$ Assuming, $u=0$ $$s=\frac{1}{2}at^2$$ $$a=\frac{2s}{t^2}$$ So I got a function for acceleration. $$v=u+at$$ $$v=\frac{2s}{t} \tag{1}$$ In reality I know that $s=vt$ when ...
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Paradox in the Kinematic Equations of Motion

The 5 equations of motion have been chosen such that from the 5 variables of motion: $s$, $u$, $v$, $a$ and $t$; each equation, exclusively omits one of these. This allows us to only ever require the ...
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Breaking distance including downforce, air etc

I would like to calculate breaking distance for car from 200km/h to $100$ km/h with acceleration $-44$ m/s. I found this: $$ V_{\rm init} = 200~{\rm km/h} = 55~{\rm m/s}~,\\ V_{\rm final} = 100~{\rm ...
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Kinematics of a 3-wheeled omnidirectional robot

Consider a 3-wheeled, omnidirectional robot (also called a kiwi drive). To see what this looks like see this YouTube video. We can control the motor speeds using a microcontroller. Task: We have to ...
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Is the Biot-Savart energy always a kinetic energy (vortex dynamics)?

I'm trying to understand the paper On Bubble Rings And Ink Chaldeliers from Padilla et al. (On Bubble Rings And Ink Chandeliers. Right now I'm reading section 3.3 Equations of motion. There, the ...
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3 answers
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How can you find average velocity from acceleration and time?

This is a question I came across in a lab report for my first high school physics course. And I'm a little stumped by it. So far the only way I know to get the average velocity is to add the final and ...
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If we know the location of object at different times, what more can we find out from it?

I'm brushing up on my physics, and I've been struggling with this problem in my head. I hope you can help. Let's assume that we have some object/particle that only moves along a single axis ($x$). We ...
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8 answers
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What's the mathematical proof of "Net velocity"?

We often calculate the velocity of a boat moving upstream as the (velocity of boat in still water$-$velocity of stream), and add them for downstream. My teacher told me that it's "net velocity&...
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3 answers
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Why the velocity vector is perpendicular to the position vector in a circular motion?

I know by definition it should be perpendicular I just don't get why
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What is the relationship between velocity and time of an object gliding through water?

I took a video of a swimmer pushing off of the wall and gliding through the water until they come to a stop. Using some video analysis software, I was able to plot data points for their velocity over ...
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1 vote
1 answer
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Non-uniform deceleration model

I encounterd a brake model for an ERTMS system (E=Europe) with the following characteristics. A point starts a decelerating proces at $t=0$ when $v=c$ but first there is a reaction time $T$ during ...
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Usage of Velocity = Displacement/Time to get the time interval at relativistic speed

Say I am in a spaceship. Another ship moves relative to me along a direction directly away from me, with a relative velocity(comparable to c) which I determine by measuring the doppler effect. My ...
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2 votes
1 answer
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What is the physics principle behind Helicone (wood toy)?

There is kind of toy "Helicone" (https://www.youtube.com/watch?v=nkmBLPHGp0E), It is composited with one base, one axle and many co-axle leaf-pairs. When rotating it in a direction and ...
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3 answers
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Do relativity and frame of reference contradict each other? [closed]

Relativity states that nature doesn't depend on how we look at things, and a physical process is the same no matter what perspective we choose to think about it in, and frame of reference is a set of ...
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Projectile motion from a height

I came across a problem in my book with this diagram, A machine gun is mounted on the top of a tower 100 m high. At what angle should the gun be inclined to cover a maximum range of firing on the ...
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1 vote
2 answers
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An overwhelming thought experiment regarding Newton's Third Law and motion of two bodies in an ideal condition

I came up with this experiment in my head. Suppose there are two blocks $A$ and $B$ in an ideal situation(no friction, gravity, air resistance whatsoever). Velocity of $A$($v_A$)=$10 ms^{-1}$ Velocity ...
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3 votes
3 answers
318 views

Relative velocity related to acceleration

Let's say we have a car moving on the horizontal ground with a velocity of $10 \hat{i} \frac{m}{s}$. A person inside throws a ball vertically upward with a velocity of $3 \hat{j} \frac{m}{s}$. Now I ...
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4 votes
9 answers
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High school physics problem - having trouble understanding

This is a fairly straightforward problem which doesn't require the usage of more than one or two formula but I find it hard to grasp the concept behind this. Let's say we have two trains, one which ...
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3 answers
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Ball trajectory inside a car with constant speed [closed]

In a car moving at a constant speed (no acceleration). The driver throws the ball in the direction of the passenger seat. Dose the ball follows the same path as if the car is stationary or it would ...
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1 answer
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Problem in resolving pursuit curve with Simulink

Reading this document I had difficulty solving a differential equation with simulink. I report the problem in case the link expires.                                                                     ...
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1 vote
1 answer
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What is the relationship between the speed of the end of the thread and the angular velocity of the spool which was pulled by the winding thread?

On a rough ground, there is a cylindrical spool of inelastic thin thread (as the picture following), the inner and outer radii are $r$ and $R$ respectively, the thin thread is wound in its inner ...
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1 answer
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Could you use a chaotic pendulum to generate energy? [closed]

Could you use a chaotic pendulum to generate energy?
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1 answer
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Relation between kinetic energy and momentum in relativity

In a recent discussion a friend of mine claimed that kinetic energy ($K$) an momentum ($p$) in relativity can me expressed by $$K=\frac{p^2}{(1+\gamma)m} \tag{1}$$ This equation if holds, has some ...
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2 answers
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Is the derivative of the magnitude of a position vector the speed? Is the integral of the speed the magnitude of a position vector?

I'm reading a book titled "Introduction to Mechanics" by Kleppner, and I came across an example: A bead moves along the spoke of a wheel at constant speed $u$ meters per second. The wheel ...
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1 answer
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Components of speed vector after bouncing of a tilted wall [closed]

Suppose a ball with velocity $v$ hits a 45 degree tilted wall at an angle $\theta$. Let $v_x$ and $v_y$ be the components of $v$ before the hit, what are the components after the hit as a function of $...
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1 vote
2 answers
118 views

One object moves along the cycloid at a constant rate, how about its acceleration? [closed]

We know that the parametric equation: $$x=R(\theta+\sin(\theta))$$ $$y=-R(1+\cos(\theta))$$ and the constant velocity $c$. How do I prove that the acceleration of the object in the $y$ direction is ...
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Acceleration in polar coordinates

Is transverse acceleration always perpendicular to the normal acceleration, in polar coordinates?
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Error when calculating velocity by numerical integration

I'm trying to do a consideration about the error obtained when we choose to approximate a discrete signal of acceleration (and the relative discrete signal of velocity) using a continuous function. ...
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1 answer
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Confusion regarding ball bouncing off a wall with respect to Newton's Third Law

This is more of a confirmation post whether my ideas are correct or not. Suppose a ball of mass $5 kg$ travelling with uniform velocity $5 ms^{-1}$ through vacuum hits a block of mass $200kg$ with ...
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1 answer
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Inertia of an elevator

Imagine a situation where we have a relatively light empty elevator moving up at a pretty high constant velocity say something above $10\ m/s$, just so that it has a considerable amount of momentum ...
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1 vote
6 answers
670 views

Is velocity a vector quantity? [closed]

I've read that velocity is a vector quantity. Then why do most of the people when stating the velocity of an object never use direction? Most of them usually say that 'a car is moving at a velocity of ...
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1 answer
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Why does my method not work? [closed]

The question is as follows. A golfer is playing golf facing an inclined plane of inclination angle $\theta$. When he strikes the ball, the ball flies towards the inclined plane. The ball left the ...
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1 vote
2 answers
109 views

How do I get the total acceleration from 3 axes, in negative?

For a project, I'm working with acceleration data recorded by triaxial accelerometers. This means that I have accelerations in the x, y, and z axes. I found the almost exact same question from a few ...
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Position vector for free fall along an inclined plane

I understand how to make a force diagram for an inclined plane. Assuming I have an inclined plane in the form of a right-angled triangle with both cathetes $k$, the angle of the inclined plane is $\...
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