# 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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### Kinematics constant acceleration problem

A stone is being thrown vertically upward with a speed of 12.5m/s from the edge of a cliff 75.0m high, what’s the total distance did it travel? It is a constant acceleration kinematics problem, I ...
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### Understanding where equation $2.3$ comes from?

I'm trying to understand this paper (equation $2.3$ specifically): Bini, D., Carini, P., & Jantzen, R. T. ($1995$). Relative observer kinematics in general relativity. Classical and Quantum ...
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### Why does the amount of rope unwound from a spool correspond to its change in center of mass?

Consider a spool wound up with rope and a person pulling the spool, in such a way that the spool rolls in that direction. I know intuitively that the amount of rope unwound equals the displacement of ...
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### Why is the complex time not considered in the solution?

In the solution, why is the the complex time not considered and real and positive time is considered? Is it because complex time does not exist or there is some other reason?
1 vote
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### How do I study for vectors? [closed]

I live in India and I am currently an 11th Grade student. I am having difficulty studying physics, specifically Vectors and Kinematics. I have Concepts of Physics Part 1 and while its enlightening, I ...
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### Query Regarding circular motion [closed]

Suppose a particle is moving with tangential acceleration of constant magnitude but with centripetal acceleration magnitude variable with time (suppose proportional to $\,t^2$). Then what does the ...
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### How to calculate total sum of orientation changes in 6 DOF data from a Motion tracker?

I'm using data from a motion tracker that give provides 6 coordinates for every frame ( with frame rate of 240Hz) Position: x, y, z Orientation: azimuth(yaw), elevation(pitch), roll I can calculate ...
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### Is friction equal to gravitational force during rolling down a ramp?

I'm studying the motion and forces involved in a ball (bidimensional) rolling down a ramp inclined by an angle $\theta$ from the x-axis. This is the body diagram (I didn't draw forces but there is ...
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### What happens to velocity if mass changes, in uniform velocity motion of a body? [closed]

If a body is in motion with some constant velocity, but its mass is decreasing as it is moving forward, what will happen to its velocity? Does it stay constant, why?
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### Linear Acceleration, Frames of Reference and the Laws of Physics

Alice and Bob, observers in deep Galilean spacetime, have identical rocket ships. Alice is at rest relative to an inertial frame. At $t=0$ she accelerates with acceleration $a_0$ in a straight line ...
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### Is there anything like negative deceleration?

I kinda understand acceleration, deceleration and negative acceleration but does anything like negative deceleration exist?
1 vote
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### On relativistic kinematics of particle accelerators

While reading these lectures I came across the following Putting together the first two formulae one reads $M=E_{cm}$, or equivalently, the centre of mass is always at rest. But is it true? It might ...
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### How to determine the units of the terms of a function relating two physical quantities?

While studying kinematics I came across a problem which said, A particle is moving along X-axis, its position $x$ varying with time $t$ as $x(t) = 2t^3 - 3t^2 + 1$. Now, that is not the full problem ...
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### Upper and lower limits of integration in the derivation of kinematic equations?

I have already read part of this answer, but I need further clarification. In the derivation of kinematic equations, the following two lines are present: Acceleration is constant. $\text dv=a\text dt$ ...
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### Peskin & Schroeder's QFT book page 167

I am wondering how to get below equation (above eq.(5.104)) on Peskin & Schroeder's QFT book page 167: $$y\simeq\frac{1}{2}(1-\cos\theta)\simeq 1-\frac{\chi^{2}}{4}.$$ Here, the book try to ...
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### Projectile motion question - finding launch angle given only range and initial velocity [closed]

this is a first year physics problem about projectile motion, which I usually am pretty good with but this question confused me because it doesn't state that the motorcycle lands on the same elevation ...
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### Proving the equivalence between max range for a fixed speed and min speed for a fixed range for a projectile

https://math.stackexchange.com/a/2663051/ In this post which was accepted as solution the answerer said "By the way, proving that the maximum range in a slope (or minimum speed to a fixed range) ...
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### Kinetic energy with respect to center of mass frame (COM) [closed]

Let there be an object having some chemicals in it. It starts moving with a uniform velocity $v$ and a chemical reaction starts happening. In this case, which of the following statement/s is/are ...
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### Generalize knowing when to accelerate towards or away from a target you are moving towards to arrive without overshooting it

Imagine you are a spacecraft moving towards a position and you start out with zero relative velocity. You accelerate towards it, then halfway there you start accelerating in the opposite direction so ...
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### I have a question about explanation of inertia of motion of a body by pseudo force

If a bus stops moving suddenly, we tend to fall forwards due to the inertia of motion of our upper body. But can we explain the sudden jerk in the forward direction due to some pseudo force? (Because ...
1 vote
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### Easy mechanic question

A man is walking down a street, he wants to avoid touching any rain drops. Walking with a velocity of $v$ and rain drops falling at $u$. He has an umbrella with radius of $r$ and his height is $h$. ...
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### What is closing speed?

what is closing speed? the only information google was able to give me, is that closing speed is when a car is approaching another car both at 30m/s the closing speed is 60m/s, so what exactly is ...
1 vote
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### Difference between geodesics on surfaces and paths under gravitiational fields

Sorry for the maybe silly question, but I'm a math student and I'm not able to find the answer to this question from the physics point of view. Let us suppose that a ball is set in a non equilibrium ...
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