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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What is displacement time graph for this object which is in $xy$ plane going in sine wave like path from A to B. Also can velocity constant in path?

The path is from A to B in sine wave curve while the displacement is straight line.So how displacement is calculated for graph purpose here
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End motion of an empty spherical shell with a ball rolling on it's inner surface

Let's picture an empty sperical shell in inter galactic space or beyond. Inside this shell, a ball is rolling on the inner surface. Because of friction and the centrifugal force the ball exerts on the ...
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How, if, does the inside air of a football influence it's motion?

And before me lies a football. Say it's filled with pressurized air. If I kick it, how will the inside air be influenced? Will the kick induce soundwaves? Can the ball give a sound? Will it influence ...
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If we put a number of identical boxes on top of each other and apply a linearly increasing force to the bottom, will they start slipping one by one?

Let's imagine the following scenario. I put a number of identical boxes on top of each other. I then apply a constant jerk to the bottom box. What will happen? Will the start to slip one by one? The ...
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Can an object move with a constant velocity without balanced forces?

Can an object move with a constant (magnitude) velocity without the balanced forces? As an object which is balanced with the frictional force continues moving at a constant velocity, acquired till ...
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How does a sliding object stop moving by the effect of kinetic friction, if kinetic friction is constant and Fk can't be greater than Fapp on its own

The kinetic friction is constant. So if say, I apply a force of 20N on an object and the kinetic friction is 13N, then how does the object stop moving after some seconds. I believe that kinetic ...
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Can't understand a statement about motion

From the book where I am studying motion, It says Motion is a combined property of the object under study and the observer. There is no meaning of rest or motion without the viewer. I know that, for ...
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Can a frame still be an inertial frame if its center varies with time relative to a “true” inertial frame?

Picture a seat on a Ferris wheel. Neglecting any rocking, is the seat of a Ferris wheel an inertial frame? My guess is that yes it is right? The frame itself isn’t rotating or accelerating relative to ...
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What is the instant velocity? [duplicate]

The velocity is the variation rate of the position correct? So does it make sense to talk about velocity without time?
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Changing velocity even when acceleration is zero

Consider a particle performing circular motion with position given by $$\vec r=r_0e^{\beta t}\hat r$$ such that $\dot\theta=\omega$, is a constant. The velocity becomes $$\vec v=\beta r_0e^{\beta t}\...
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Projectile launch question [closed]

The question refers to the following information: What would the Olympic Games on the Moon be like? This article was recently published in the magazine Mundo Estranho, Editora Abril, written by Tiago ...
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Vectors in different coordinate systems [closed]

The answer for the first question is "The wind blows from $40.5^\circ$ NE". But I think it is impossible. The following is how I do the first question. Set that $\mathbf{i}$ is the unit ...
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Why doesn't an air valve move automatically when placed on a zero friction surface?

Air pressure is actually a force experienced by the surface of the container when air molecules hit it in high speeds. An air valve opens and allows air to move in one direction and blocks the the ...
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Why do kinematic equations only work with constant acceleration?

People say that the equations are derived assuming a constant acceleration. I just don't see how this is the case. (I am new to calculus.)
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Why do equation of motion fail to apply in non-inertial frame even after applying pseudo force?

I considered two cars of equal mass moving towards each other with speed 30m/s and 18 m/s respectively and when they are 100 meters apart they both start de accelerating at 6m/s² each. So if we ...
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Minimum seperation of moving objects doubt

Let there be $2$ objects $P_1$(initial velocity $u$ $ms^{-1}$ & acceleration $a$ $ms^{-2}$) & $P_2$ (initial velocity $U$ $ms^{-1}$ & acceleration $A$ $ms^{-2}$) initially separated by ...
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Can the speed of the wind influence the speed of sound propagated in it?

The question came up with a exercise (Page 5, exercise (vi) of Pratice Exercise 1.1) from the book Physics Galaxy Volume 1 Ed. 1, Ashish Arora. The question proposes the following: Two junglemen are ...
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Why power of engine must be equal to power of friction?

Suppose a car with electrical engine moves uniformly with friction between wheels and the ground (neglect air resistance, energy loss, etc.). So why the car's engine power must be equal to friction's ...
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Strange kinematics result

I'm currently doing some algebra-based physics problem sets and have come across this strange result. Problem A ball is tossed upwards with an initial velocity $\vec{v}_0 = 48.9\text{ m/s}$. Assuming ...
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Lagrangian Dynamics of an inverted Spherical Cart Pendulum

Introduction I have to come up with a PD-controller for an inverted Spherical Cart Pendulum, therefore I tried to compute the Dynamics of such a Pendulum. The Spherical Cart Pendulum is a hybrid ...
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A question regarding equations of motion

Suppose I drop a body from a height $h$. The initial velocity is zero. Now it reaches the ground and stops and finally becomes zero. So now u=0 and v=0. If I use the equation of motion $v=u+at$ to ...
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How to find time taken for a faster object to cross a slower object of same length, both moving parallel to each other in the same direction? [closed]

Can you explain me how to determine the time taken for a faster object to cross a slower object when they're both of same length and are moving parallel to each other in the same direction?
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Is the deceleration a result of friction, a constant value?

Frictional Force = km, therefore k = a Would this mean that no matter the mass of an object (if they are the same material) They will decelerate at the same speed with friction, therefore if u is the ...
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Angle-free two-dimensional inelastic collision formula?

I'm trying to calculate velocities (by components - x, y) of two objects (balls) after inelastic, two-dimensional collision. I've successfully implemented the angle-free formula for elastic two-...
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What happens to the motion of the body if acceleration equal zero? [closed]

$If$ the body moves with $variable$ velocity and $variable$ acceleration ,but at a certain instant the $acceleration$ was zero then we can say at this instant the body moves with constant $velocity$ $?...
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Find the equation for the angle $\theta$ in which the particle leaves the semicircle. No Friction [closed]

I think I missed something in this mechanics problem. We're given a polished (no friction) and homogeneous hemicircle which has mass $M$ and a particle of mass $m$ laying on the top of it. There is ...
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Does the kinetic energy theorem imply that any body on wich is exerted the same space-dependent force is equally accelerated?

So, we have a body $P_1$ of mass $m$ that travels from $A$ to $B$ along a straight line, on wich is exerted a constant force $F$ dependent only on the position of $P_1$. We know that the work done is $...
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How do we assume the direction of $u_{\theta}$ and $u_{r}$ in polar coordinate systems?

Is there a way to correctly predict the direction of the unit radial vector and the unit transverse vector in problems like the one below or is it just better to take a guess and solve the problem ...
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Projectile with air resistance analysis

If a projectile is thrown neglecting air resistance, then the horizontal distance covered by it in ascent and descent is same. if we consider air resistance, then i want to compare horizontal distance ...
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Does tangential velocity not change the "radial displacement"?

For example, we have two point masses U and V moving like the picture below with constant velocity. Is the change on "relative position" in this case only affected by the velocity $u$ and ...
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Minimum energy of projectile to trigger a nuclear reaction and energy of ejectiles

I am studying the following type of nuclear reactions : projectile+target -> ejectile1+ejectile2 I make the assumption that the target is static. This reaction needs energy to be triggered (Q-value&...
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Closing speed and time needed for light to reach moving object

I've come across this kind of problems where I need to find a time interval for light rays to reach a moving observer. Suppose Bob is travelling towards a mirror at a speed $v$ relative to the mirror. ...
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Finding How to Transform a Plane to Reflect a Trajectory through a Given Coordinate

So, for context, I am trying to analyze how this basketball machine works: https://www.youtube.com/watch?v=FycDx69px8U I have a basic understanding of how to calculate the new velocity of the ball ...
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Simple harmonic motion in uniform circular motion as a projection along $x$-axis

The image shows the position of particle at $t=0$ and $t=t$, and the relevant angles are labelled. The radius of the circle is A. When I try to find $x(t)$ I can directly resolve along the negative $x$...
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Trajectory with non-trivial barrel length taken into account

I have pretty much the same question as this: Finding the Angle of Launch for a Cannon Projectile to Hit a Specific Point It wasn't answered back then, and I only found it after I made my own initial ...
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How to simplify three body decay phase space in terms of invariant mass $q^2$?

We know three body phase space is written as: $$\mathrm d\pi^3 = \frac1{2M_1}\frac{1}{(2\pi)^5}\int\frac{d^3 p_2}{2E_2} \int\frac{d^3 p_3}{2E_3} \int \frac{d^3 p_4}{2E_4} \delta^4(p_1-p_2-p_3-p_4)$$ ...
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Calculating the rest mass after relativistic collision [closed]

Suppose we got two particles, both of mass $m$ for simplicity, travelling at high speeds towards each other, meaning we have to take into consideration of relativistic effects. We also know that the ...
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Angular velocity of a particle in uniform circular motion about a general point

This problem was given by our professor. Consider a particle P executing uniform circular motion wrt the point O with uniform angular velocity $\omega$ anticlockwise whose cordinate is $(2R,0)$ in a ...
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Simple 1D Motion Problem

I am having a friendly debate with someone regarding the solution to a 1D motion test problem we both came across. It goes something like this (numbers changed to preserve integrity of test material). ...
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Vehicular Dynamics [closed]

Consider an open differential connected to two wheels on each side. The wheels are flat discs and are 1400 mm apart. This car is making a turn of radius 7 m at a constant angular velocity of 30 ...
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Can a particle move in an upward parabola fashion naturally?

I recently studied projectile motion which consists of only downward parabolas. But I was wondering whether is it possible for a particle to go in a upward parabola provided that the particle doesn't ...
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Calculate Projectile impact with a moving Target [closed]

I'm trying to solve the classic shoot moving object issue in 3D Space, but with acceleration and gravity added to it. I already tried several ways approaching the correct calculation, yet I face the ...
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How is the angle of the front wheel found in Bicycle Kinematics Model for a Car

My question is, in a 4 wheel model, the front wheels have different angles. To simplify things bicycle model is used. In the bicycle model, there is an imaginary wheel in the middle of the front ...
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Is a reasonable assumption to consider that the contact point of the Euler's Disk (with stationary center of mass) trace this finite bounded spiral?

Is a reasonable assumption to consider that the contact point of the Euler's Disk (with stationary center of mass) trace this finite bounded spiral? This question is highly related to working with the ...
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What do you call $ \frac{d^2 r}{dt^2}$ in polar coordinates? [duplicate]

In polar coordinates, one finds centripetal acceleration as: $$ a_c = \frac{d^2 r}{dt^2}- \frac{v^2}{r}$$ Where $|r|$ is distance from center to particle, $v$ is tangential velocity. My question is ...
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Calculate efficiency from discrete power, time and distance

I have a sequence of points from GPS and OBD for some vehicles. Each point has the instantaneous power of the engine $(P)$, the time elapsed from the last points $(T)$ and the distance traveled from ...
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3 answers
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Existence of uniform circular motion [duplicate]

We know that if any body has some mass and is moving with a velocity v at an instant $t = 0$ , then it is not going to have same velocity after some time if any net force acts on it. It is because the ...
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How to interpret a displacement-position graph?

I have a good understanding of Displacement-time graphs and position-time graphs and how to interpret them. I take the IB diploma and came across this question from a 2009 paper with a displacement-...
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Related bubble questions: In water vs air, what causes bubbles to form?

One thing I would guess would happen is that air released under water would diffuse through it as individual molecules rather than collecting as bubbles. I suspect the bubble effect might come from ...
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Kinematics of a rolling disk on a static disk (variation of the Euler disk)

I'm puzzled by the following problem. Consider a simple tilted disk $\mathcal{D}$ of radius 1 (in any unit) rolling without sliding on top of a static horizontal disk $\mathcal{S}$. The normal $\...
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