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# 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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### How to calculate/use Horizontal Coefficient of Restitution value for basketball?

I'm trying to run an experiment in which a basketball is dropped straight down with a certain angular speed and then undergoes a bounce. My goal is to create a relationship between the initial angular ...
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### How to prove the relativistic momentum?

As far as I know, the relativistic momentum of a particle is given by the equation: $$p=\frac{m_0v}{\sqrt{1-\frac{v^2}{c^2}}}$$ where $m_0$ is the mass of the particle and $v$ is the velocity of the ...
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### Energy consumption from acceleration

I have an interesting problem. I have a machine which has to lift 35 kg (this is the total mass of the object and the lifting arm). The lifting is done by a servo motor. Now I want to calculate the ...
269 views

### Is there some intuitive way to think about imaginary time?

When acceleration is constant, then distance is a quadratic function of time. So, the solutions can be complex numbers, right? I can intuitively think of negative solutions like this: If my scooter ...
239 views

### Can a car with a high center of gravity and front and back wheels close together lean while its stopped

I dont own the first 3 pictures Imagine a car with a high center of gravity and front and back wheels close together. Similar to this. This is the car before moving. Ignore the force arrows. It ...
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### Angles of projectile motion [on hold]

A soldier decided to hurl a ball of mass 40kg somewhere 400m away. If the maximum range is 500m, find the angles of projection. I can't seem to get my head around this one. I tried to find vertical ...
22 views

### Determine displacement and time graphing

How to plot $d$-$t$ graph from $v$-$t$ graph?
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### Determine angle of propulsion [on hold]

Fuel is burnt to propel the missile, if propulsion provides a constant acceleration of 40m/s, determine the angle that missile must be angled to make it fly at a constant height. Not sure what to do ...
22 views

### Generalization to Rear-Wheel Steering?

Given the position of the vehicle (𝑥,𝑦) at different time points, the speed of the vehicle (m/s), the direction the vehicle is facing (heading — in degrees), the track width of the vehicle, and the ...
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### How does the force on a crashing train relate to its velocity and the area of the train that is touching the wall?

I am modelling the crashing of a train with a deformable crumple zone on the front. I am assuming that the crumple zone deforms from the front back, so I am essentially modelling it as if the crumple ...
52 views

### Acceleration-time graph for a falling object

I understand that when drawing an acceleration-time graph for a falling object (with initial velocity = 0), the y-intercept should be $9.81ms^{-2}$ and acceleration should end up being $0ms^{-2}$ as ...
56 views

### Distance traveled by a particle in $n^{th}$ second

My book states that the distance traveled by a particle thrown upward in the last second is independent of it's initial velocity because the the object travels the same distance as a freely falling ...
2k views

### When the direction of a movement changes, is the object at rest at some time?

The question I asked was disputed amongst XVIIe century physicists (at least before the invention of calculus). Reference: Spinoza, Principles of Descartes' philosophy ( Part II: Descartes' Physics, ...
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### Physical interpretation of complex numbers, part 2

I walk in the x direction, if I walk twice as fast, 2x, if I walk backwards, -x. What about ix? If I say that I walk an imaginary distance ix then this means in physics and maths that I walk ...
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### Why is the normal force equal to zero at the top of a rollercoaster if the speed is the minimum?

I was practicing for one of my physics exams and there was a problem that asked for the minimum speed a rollercoaster would have to go for its riders to not fall out at the top of a loop. I did the ...
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### Is there any physical evidence for motion?

Let's say that we have 2 tennis balls in space, one being in motion (say, pushed by an astronaut), and the other one still. If we could take a snapshot of both tennis balls, would there be any ...
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### Does super position precede physical phenomena?

If a traveling wave has amplitude of d, it feels certain amount of force at that moment in time when it is displaced for equilibrium. Thus there is also strain on the string corresponding to that ...
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### Moving an object which is at rest on the floor

A block for example, its net force would be $0$. I am imagining a scenario where I apply a vertical force such that $0<F<F_g$. The way I understand it is that this, theoretically, means that, ...
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Suppose you are moving in circle of radius $r$. So there should be centripetal acceleration towards the center. Now you want to decrease the radius of the circle, so someone should apply more ...
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### Physical Interpretation of an Elementary Inequality in Kinematics

I recently came across the following question: suppose a point mass moves a distance $d_1$ for $t_1$ seconds at a velocity $v_1$, then accelerates instantaneously to a velocity $v_2$ and travels a ...
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### Kinematics and Acceleration Windows

I am a CS student who is currently programming for a robotics project. The kinematic physics at play has me a bit confused, and I am wondering if someone can provide some clarity on this problem: I ...
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### The physics of board breaking

Pardon my really rusty school physics knowledge. I heard martial artists talking about the physics of board breaking and one of the things which they mentioned is formula "F=ma". They were talking ...
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### Finding the distance traveled by a jet [closed]

QUESTION (The following question is from Physics NCERT, standard textbook in India) An aircraft is flying at a height of 3400 m above the ground. If the angle subtended at a ground observation ...
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### Motion in two and three dimensions [closed]

At time t = 0, a burrito is launched from level ground, with an initial speed of 16.0 m/s and launch angle 0. Imagine a position vector -continuously directed from the launching point to the burrito ...
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### Why we take only the vertical component of a projectile's velocity while calculating the “Time Of Flight”?

when we calculate the time of flight for projectile with no drag we use second equation of motion i.e. $$S=V_i t + at^2/2$$ further, we put $V_i=V_i\sin\theta$ and $a=-g$ i.e.: S=V_i t\sin\theta - ...
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### simulating partially inelastic collisions [duplicate]

I have an abstract problem that I am trying to wrap my head around. I understand that to solve the problem of the final velocities in a perfectly elastic collsion, you can determine it using the ...
54 views

### Are both kinetic energy and momentum conserved when 2 objects undergo a collision? [duplicate]

for example when two objects undergo a collision and no external force is acting on them. Will both kinetic energy and momentum be conserved or just momentum?
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### Instantaneous Velocity at a Sharp Point

My friend and I are having an argument. Here's the situation: A block is at rest on a frictionless surface. At instant $t_0$ a person pushes the block to the right with a constant force. At instant ...
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### How much force is necessary for a crowded bus to get out of inertia

I have always wondered how much force is necessary for a crowded bus or train to speed from 0 km/h to 20 km/h, and compare it to some known figure, like a great white shark bite. This curiosity hits ...
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### How to Find Jerk from Discrete Velocity Data?

I have measured the velocity of an object at discrete intervals. I want to find the corresponding acceleration and jerk of the object. How do I do this with discrete values rather than continuous ...
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### How do I interpret/make sense of $\frac{d\theta}{dt}$ in physics’ language?

Here’s a question from my textbook. It’s a simple question that involves a little bit of calculus. I was able to solve it. But what I don’t understand is, I could not fully understand the final result....
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### Graph for Vertical Velocity of an airplane

I'm a fresh Calculus $1$ student struggling to make this graph somehow, I've been studying Chapter $1$ from James Stewart's single variable Calculus early transcendentals. Excercise $1.1$ is easy up ...
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### Period of mass in circular motion [closed]

I've been trying for 4 days now to solve my physics lab assignment but now I'm starting to think there must be a mistake in the question. You know those rotating mass experiments where you have a mass ...
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### Shooting a glass made different with water!

I read about an experiment conducted long back ago. The experiment tells that shock waves are the reason for this. The experiment goes like this, shooting a drinking glass with bullet then bullet ...
173 views

### Calculating mobile displacement based on acceleration

I have written a mobile app that measures x y z accelerations. I am trying to convert the acceleration results into displacement but dont think a simple $d=\frac 1 2 {a {t^2}}$ will do the job. We ...
3k views

### Pushing down on the gas pedal of a car a good example of jerk?

I'm trying to think of the clearest examples to demonstrate the concept of jerk to a layman. Ignoring drag and making other reasonable assumptions (friction is conveniently there to only allow you to ...
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### The dropping of two identical balls without air resistance [closed]

I was thinking about this and couldn't really figure it out. You are standing on a cliff and you have two identical balls. In this case, air resistance is to be ignored. The only thing different is ...
175k views

### How can momentum but not energy be conserved in an inelastic collision?

In inelastic collisions, kinetic energy changes, so the velocities of the objects also change. So how is momentum conserved in inelastic collisions?
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### How is Chasles' Theorem, that any rigid displacement can be produced by translating along a line and then rotating about the same line, true?

Chasles' Theorem in its strong form says: The most general rigid body displacement can be produced by a translation along a line (called its screw axis) followed (or preceded) by a rotation about ...
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### Is acceleration continuous? [duplicate]

The extrapolation of this Phys.SE post. It's obvious to me that velocity can't be discontinuous, as nothing can have infinite acceleration. And it seems pretty likely that acceleration can't be ...
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### The distance of an object undergoing constant acceleration

Is the distance an object moving increases with time if it is accelerated with a constant rate? I mean, doesn't it depend on the direction the object is traveling? if I throw an object upward, ...
While going through my physics book, I got over a question which ask us to plot a position-time graph for the interval ($t=0\,\mathrm s$ to $t=5\,\mathrm s$) From the top of a tower, a ball is ...