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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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Finding the equations of motion with observations

Let's say that we don't know the equations of motion. I will try to predict where my ball will fall when I shoot it with an angle $\alpha$ and and speed $v$ by finding the function that describe this....
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0answers
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Projectile motion launched at an angle and landing higher than start

If a projectile is launched from the floor, and lands at an elevated height how would one find the initial velocity given only (angle of launch, angle of ending elevation, total distance, and gravity?
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1answer
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Kinematics lessons involving calculus [on hold]

Does solving instantaneous velocity involves calculus in kinematics? What are the other lessons or unknown variables in Kinematics that involves the use of Calculus? What are the other lessons also or ...
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2answers
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What would the position vs. time graph look like if the velocity vs. time graph was a curve?

In my physics class we are learning about velocity vs. time graphs and position vs. time graphs for an object. We have learned that if the object is moving with constant velocity (this would be a ...
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1answer
46 views

Simple Kinematics question [on hold]

So this is a pretty simple kinematics question I was working on but I completely skipped over a derivation. Here's what I did to solve for the first part: I'm wondering if there is anyway to solve ...
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0answers
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I'm clueless, need help [on hold]

Easy problem but I'm clueless about my approach
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1answer
26 views

How to calculate the needed Pa to penetrate a defined thickness material

I am currently doing research for a video game I am developing, right now I am trying to figure out how to calculate how far a bullet will penetrate a plate of metal. I just need the bare bones ...
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1answer
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Determining $v(t)$, time taken and distance covered by a plane given $a(v)$. Plus, reason why it is unreasonable.

GIVEN PROBLEM: A jet plane landing on an aircraft carrier deploys a parachute to slow itself. The acceleration achieved is $a=-0.005v^2 m/s^2$. a) If the initial speed of the plane is $60 m/s$ ...
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1answer
23 views

Kinematics Problem requiring Calculus [on hold]

Let the Instantaneous Velocity of a rocket just after launching be given by v={ 3t for 0<= t <2 2t+ 3t^2 for 2<= t<=3 t^3 for t>3 Find the ...
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1answer
45 views

Silly question about velocity

I know that velocity of a particle moving along a curve at a given point in time is tangential to a curve. I can also tell why intuitively. Also I am familiar with the experiment of spinning a ball ...
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0answers
27 views

Problem with calculating electron proton scattering cross section (mott formula)

This is probably obvious, but I can't figure it out. (In particular I am trying to reproduce formula (13.103) from Matthew D. Schwartz's QFT book). We have $e^-p^+ \rightarrow e^-p^+$ scattering, so ...
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1answer
28 views

Time taken by falling body and Force via pulley? [on hold]

Hi guys, I have 2 simple questions. If you refer to the image you can see 2 figures. In Fig.1, I managed to calculate the time taken for a falling body via SUVAT. But I want to know how to calculate- ...
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3answers
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How would a fast-moving atom interact with a body? [closed]

I found this question on Quora: https://www.quora.com/Can-you-theoretically-shoot-an-atom-fast-enough-to-kill-its-target I think the Quora answer is good but incomplete, and it got me wondering what ...
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1answer
34 views

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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0answers
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Is it possible that D-T graph could be linear , but V-T graph will be log?

So , I have plotted the V-T & D-T plots for solar sail using the parameters (Using euler's method for solving the ODE based on Solar sail, estimate force & Here's my program :- https://github....
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0answers
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Find acceleration [closed]

Particle is moving along positive x direction with constant acceleration the graph between average velocity and time is given Then acceleration will be
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1answer
91 views

How does this magnetic toy work?

A nephew of mine has this toy called "Gravitrax". It is basically a track building kit - you can build various tracks for iron balls which go through the track thanks to gravity. However, there is ...
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0answers
23 views

How will I find the final velocity when acceleration and deceleration is given? [closed]

An object initially rest starts accelerating with acceleration=a and after sometime it starts decelerating with accelateration=-a. If the total time of motion is t then find the the maximum velocity ...
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3answers
44 views

How to know which constant acceleration equation to use? [closed]

The question I'm working on: This is the answer: For (b), I just want to know why we use ((v+u)/2)t) to find the displacement of the mailbag. It is clearly a free falling object that has ...
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0answers
80 views

My physics teacher and I disagree on the answer to a problem. Who's right? [closed]

Recently, I got a test back from my physics teacher and we were given an opportunity to correct it so naturally, I asked about the part I got wrong. He showed me how he answered the problem but after ...
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0answers
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Ball dropped from building question

So in one of my physics books, under the free fall section, it was written A ball is dropped from a building of height $h$, speed $u=0$ and it reached ground after time $t$. From the same ...
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1answer
62 views

Kinematics in 1D [on hold]

I was doing a problem of kinematics, which is as: A balloon starts rising upwards with constant acceleration a and after time $t'$ second, a packet is dropped from it which reaches the ground after ...
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2answers
37 views

Momentum in the rest frame

I am a little confused over the terminology of the rest frame. Say a photon collides with a massive particle then from the rest frame of the massive particle would it be the photon or the particle ...
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1answer
27 views

Calculate the distance covered by a balloon in 10seconds [closed]

Here's my problem: A balloon starts to move upward from rest with acceleration. The balloon has mass of 500 kg and volume of 600 cubic meters. I am prompted to find out distance covered by the ...
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1answer
36 views

Finding the drag force from the final velocity of a falling object

I know the velocities (v) of an object after it fell for respective distances (s). From that alone, is it possible to calculate the drag force at a specific moment in time? If not what else would I ...
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1answer
16 views

Average Velocity Question (isolation?)

So there is this question i've been having trouble with for the past hour. It involved a child going down a ramp on a sled at and angle theta with a total system of mass. accelerates down a hill of ...
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2answers
33 views

Calculating Vertical Velocity [closed]

" A salmon jumps up a 1.9m waterfall to reach its' spawning grounds" The question asks to determine minimum vertical velocity needed to reach the top." Since it didn't mention time, I tried to use: $...
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1answer
82 views

What does speed of an object relative to water mean?

A swimmer swims with the velocity 1.25 m/s "relative to water". He has to swim across the river which is 150 meters wide. If his direction of velocity is perpendicular to the stream, he is taken away ...
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2answers
567 views

Can a free particle ever emit a particle?

I have found this question here Can a free particle absorb/emit photons?, along with other resources that show a free particle cannot emit a photon (in a vacuum). Now, I am 90% sure it does, but ...
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1answer
56 views

Distance Travelled by a Projectile [closed]

I was trying to find the distance travelled by a Projectile during its time of flight, $t=\dfrac{2u\sin \theta}{g}$. I used the Equation of the Path i.e. Trajectory and built up the Arc Length ...
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2answers
26 views

Projectile Motion with Horizontal Variable Acceleration?

I am a High School Student and I've started to learn about Projectile Motion. One of the Assumptions made in the text is that the horizontal acceleration must be $0$ for the Equations of Projectile ...
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1answer
61 views

Invariance vs. Conservation of the Four-Vector Dot Product

This question refers to example 3.4 of Griffiths Introduction to Elementary Particles Second addition. In the example, a moving proton is collided into a proton at rest, producing 3 protons and 1 ...
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5answers
90 views

How to determine the direction of a vector?

I have been learning about vectors and acceleration recently and I still don't understand how to determine the direction of a vector. For instance, if we consider a freely falling particle and ...
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2answers
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Dimensional analysis on kinematic equation [closed]

I have tried to do dimensional analysis on the equation $v=u+at$. It has resulted in $v=2\,\mathrm{ms}^{-1}$. However, the units of velocity are clearly just $\mathrm{ms}^{-1}$. What have I done wrong?...
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2answers
31 views

How to change a formula when changing the axis?

I have been lerning about acceleration and free fall recently, and we were told the formula for distance is $s=s_0+v_0t+\frac {1}{2}at^2$ (for movement along $x$-axis) but when we change the axis (to ...
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0answers
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Meson scattering amplitude in the linear sigma model

I am trying to calculate scattering amplitudes with linear sigma model Lagrangian, given as $$\mathcal L= \frac{1}{2}(\partial_{\mu}\sigma)^2+\frac{1}{2}(\partial_{\mu}\vec{\pi})^2-\mathcal U(\sigma,\...
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4answers
85 views

$E=hf$ true for all implies $E=pv$ true for all?

In the answer to this question: Can I apply $E=hf$ to a particle having mass? It was stated that $E=hf$ is true for all particles. If so, doesn't this imply that $E=$momentum x velocity is true for ...
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1answer
50 views

How to know what the area under curve represents?

Is there a way to find out what the area under the curve represents? For eg. If i gave you a graph of $v$ with respect to $t$ would you be able to tell me what the area under the curve represents ...
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5answers
35 views

Why do objects move back after collision?

When a ball collides with a wall, the ball moves in the opposite direction, why does this happen if Newton's third law operates. I mean the ball collided with the wall and imparted a force on it and ...
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0answers
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How to calculate stopping distance with only negative acceleration and initial velocity?

A question on our Physics Exam Review asks for stopping distance but only gives us these two values, 100 km/h and -5.40 m/s2. Any help would be appreciated, this year's class has been a bumpy ride ...
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1answer
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The motion of an object in a slant surface against friction

if I take to surfaces slant at the same degree wouldn't there coefficient of friction be different depending on the nature of the surfaces
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2answers
80 views

How is $\int \frac{d^{3}\mathbf{p}}{(2\pi)^3}\frac{1}{2\sqrt{|\mathbf{p}|^2+m^2}}$ manifestly Lorentz-Invariant?

When writing integrals that look like $$ \int \frac{d^{3}\mathbf{p}}{(2\pi)^3}\frac{1}{2\sqrt{|\mathbf{p}|^2+m^2}} \ = \int \frac{d^4p}{(2\pi)^4}\ 2\pi\ \delta(p^2+m^2)\Theta(p^0) $$ it is often said ...
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0answers
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Relativistic energy conservation in meson decay

I'm researching special relativity, and as such am trying to do some problems to test my understanding. More specifically I am looking at pion decay of 12GeV pi+ mesons. The scenario is as such: My ...
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1answer
37 views

Kinematics Physics [closed]

A car travels between two cities , half of the time it travels with v1=ct and the other half with v2=ct . The angle between v1 and v2 is ϴ. What is the average velocity of the car?
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2answers
51 views

Range of a projectile

My notes say that the range of a projectile is equal to $$\sin(2\theta)(V_0^2/g) .$$ This equation implies that a ball shot at $0$ degrees has zero range but this isn't true is it? If I kick a ...
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1answer
34 views

Calculation of air resistance

I have a question over the calculation of air resistance. When you're calculating the air resistance of a bullet, it's velocity is decreasing over time. The air resistance is also dependent on the ...
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2answers
81 views

Inconsistent Results with Momentum and Kinetic Energy

A speed skater with a mass of $m_1$ kg is moving at $v_{1i}$ m/s. He prepares to push the next speed skater of mass $m_2$ kg moving at $v_{2i}$ m/s. After the push, the velocity of the first skater ...
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0answers
97 views

Which ball reaches the end first? [closed]

This question came up in a physics paper: there are two tracks A and B, with the direction of gravity specified. If two balls begin to move at the same uniform velocity at the same time, which of the ...
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0answers
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How does a ramp's inclination angle determine the final speed of the object (neglecting air resistance)?

If you just had a ramp at a certain angle, an object from the top of it would fall down at a certain velocity. If you increased the inclination angle, the object from the top of the ramp would still ...
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1answer
25 views

Falling object and the side wind

I don't have a big knowledge on Physics so I'm sorry in advance if it doesn't make sense.. If a brick is falling from 100m tall-building when there's the side wind of 30m/s, is there any way I can ...