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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23 views

How do I find the co-ordinates and speed of this particle on the x-y plane? [on hold]

I got this question from an old physics exam paper. I'm trying to use the kinematics equations to solve this question but the x and y co-ordinates keep confusing me. Here's the question: A particle ...
2
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1answer
32 views

A couple of questions regarding work to velocity exchange [on hold]

I was tasked to express the velocity of the cube of mass $m$ at point B using the constants given in the picture below. Friction could be ignored, and the cube could be presumed to reach B with the ...
-4
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0answers
28 views

Problem - Escalator [on hold]

I need help in resolving the following problem: On a recent weekend, Anna was rushing through a shopping centre doing her shopping she had occasion to use the escalator 3 times. The first time the ...
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1answer
19 views

a question on work and kinetic energy [on hold]

A bullet has a mass of 0.02kg and is moving with a speed of 10m/s. It can penetrate 10cm of a given target before coming to rest. If the same target is only 6cm thick, what will be the speed and ...
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0answers
34 views

3 Particle problem with a difference

Please read this completely, it is not the typical question you expect. 3 particles are at the corners of an equilateral triangle with side a. Assume that particle 1 is at (0,0), particle 2 is at ...
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0answers
30 views

Finding the distance a spaceship would travel given a time of departure and velocity

Let's say a spaceship leaves Earth at a day t and with velocity v. Is there a way to know how many kilometers it will cover to arrive on Mars? This would be a trivial question were it not by the fact ...
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1answer
41 views

Difference between classic velocity and spatial velocity

I am reading a tutorial about a physics simulator I am using, and it has the following code (in C++, but not important): ...
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2answers
50 views

Free body diagram with forces of friction

I'm reallizing that I'm very confused on how to make a free body diagram of forces in some situations where there is friction between two objects. I'll make an example where I cannot figure out what's ...
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1answer
55 views

Relative velocity of a boat traveling on a river [closed]

I am confused about relative velocity. So suppose a boat is traveling upstream on a river and a crate is dropped overboard. The boat continues to travel upstream for 60 minutes and reaches a ...
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0answers
25 views

Could someone please provide what each of these motions mean and provide a formula to it? [closed]

Each time I try to organise each of the motions separately, I get somehow somewhere confused along the way and keep on getting stuck. The following motions: Average distance Average displacement ...
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1answer
32 views

Use of the chain rule in kinematics problems for quantities given in function of the position [closed]

I don't understand the use and the meaning of the application of the chain rule in some situations. For istance, consider a 2D motion and the equation of trajectory described by a point $y=f(x)$. ...
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1answer
19 views

How fast does a long object bent at the center need to be travelling in order to boomerang?

At an angle, of course. Standard pressure, average temperature, and calm wind. Bonus question: Can an object that is not bent boomerang at all? If yes, how different would the equations for this ...
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1answer
36 views

a problem on circular motion [closed]

Question:A cyclist is riding with a speed of $7.5$ m/s. As he approaches a circular turn on the road of radius $80m$, he applies brakes and reduces his speed at the constant rate of $0.50$ m/s every ...
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0answers
56 views

How to Calculate the Distance from Lightning? [closed]

It is a dark and stormy night, when suddenly you see a flash of light. Three and a half second later you hear the thunder. Given that the speed of sound in air is about 340 m/s, how far away was the ...
-2
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1answer
72 views

What's the formula for the speed of an accelerating car?

I am trying to find a formula that closely describes the speed of an accelerating car over time. I have found many graphs on the internet, but so far no formulae to generate them. For my purposes I ...
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1answer
64 views

Does this count as a proper derivation of the formula for work and kinetic energy? [closed]

$v_{av}$ = average velocity, $d$= distance, $a$ = acceleration, $m$ = mass Given: $$v_{av}*t=d$$ $$t=\frac{v_f-v_i}{a}$$ $$v_{av}=\frac{v_f+v_i}{2}$$ Then: $$\frac{v_f+v_i}{2}*\frac{v_f-v_i}{a}=d$$ ...
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2answers
45 views

How to interpret the equation of motion of a point that changes its acceleration

I'm trying to understand more deeply the equations of motion for a constantly accelerated 1D motion. Consider a point that moves with constant acceleration $a$ and that, at a certain moment $\tau$ ...
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1answer
47 views

Relationship $v_A^2-v_B^2=2a_t\Delta s $ for motion with constant tangential acceleration [closed]

I can not understand a relationship in the general motion in the plane. I am considering a point, which follows a curved trajectory. Indicate A and B two different position of the trajectory and $v_A$ ...
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4answers
58 views

Introductory physics: first second of free fall

While doing my physics homework I encountered an acceleration problem that I've been unable to solve. Here, is the data table of the objects motion. At 1 second, why does the "Dist-meters" slot of the ...
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1answer
45 views

Finding angle between two displacements [closed]

Consider two displacements, one of magnitude 6 m and another of magnitude 8 m. What angle between the directions of this two displacements give a resultant displacement of magnitude (a) 14 m, (b) 2 m, ...
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0answers
11 views

Calculating the distance of a piston from the crank center

I stumbled upon this [https://en.wikipedia.org/wiki/Piston_motion_equations#/media/File:Piston_motion_geometry.png ] and was wondering, if you can determine the position of the piston (x) by the law ...
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0answers
27 views

How to find tangential and normal unit vector to a trajectory from the equation?

Considering a 2D motion in a plane and the equation of the trajectory of a point $y=f(x)$, I don't understand how exactly $\frac{\mathrm{d}y}{\mathrm{d}x}$ can be used. In particular if I'm looking ...
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2answers
51 views

accelerating and non accelerating duality of matter

Kinetic energy of any object , assumes accelerating nature of the object as it is derived from equations of motion for uniformly accelerated objects and the work-energy theorem which deals with ...
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0answers
44 views

What happens if an aeroplane travels in a pilot mode in a straight line with no stop? [closed]

Ex. If a plane flew upwards straight it would reach outer space but what happens if it travels below the horizon in a straight line. Will it be traveling around the earth? How? And what about it if it ...
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0answers
14 views

Relations between unit vectors in polar and curvilinear coordinates

I'm a bit confused about the relations between unit vectors in curvilinear and polar coordinates in a plane. Let $u_{R}$ be the radial unit vector in polar coordinates and $u_{N}$ the normal unit ...
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0answers
12 views

Calculation max speed for a particular speed profile, distance and time?

For work I have to calculate the maximum speed for a machine. The machine has a certain speed profile which must be followed. Besides this this speedprofile has to be followed within a certain time ...
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0answers
24 views

Is there a way to find the optimal angle to launch an object to get maximum distance when there is an initial height? (Projectile motion) [duplicate]

I know that the optimal angle to launch an object at ground level is 45 degrees; however, i want to know that if there is anyway to get the optimal angle to launch an object to get the maximum ...
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2answers
31 views

(+)/(-) Acceleration & (+)(-) Velocity

Does a negative acceleration mean an object is slowing down? Does a negative velocity basically mean you are moving at an opposite direction? The sign is just direction?
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0answers
11 views

Height estimate by step profile?

With so many current apps in mobiles tracking number of steps based on analyzing the accelerometer's measurements in time during a walk, I was wondering the following: Would it be possible to ...
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2answers
42 views

Motion of an object in a moving car and collison

I came across an interesting question today at work. 'Imagine traveling in a car. The passenger has a glass bottle in their hand. In which direction relative to the moving car should the passenger ...
4
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1answer
27 views

Transformations and kinetic energy

From the equation $E_k=\frac12mv^2$ you can determine more energy is necessary to accelerate a mass the higher your initial velocity is. For example, three times more energy is necessary to accelerate ...
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1answer
54 views

Two Trains Relative Motion

I am confused about finding the solution to this relative motion problem: You are on a train traveling east at speed of 20 m/s with respect to the ground. Your friend is sitting on another train ...
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1answer
22 views

equation for velocity vs displacement for nonlinear acceleration [closed]

An object starts out at t=0, s=0 and accelerates with A=sin(pi*t/T), where T is defined as (pi/2 * Vmax/Amax). Vmax is maximum velocity, and Amax is maximum acceleration. Solution is restricted to ...
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1answer
38 views

How does Newton's 3rd Law work in this scenario? Why is my reasoning wrong?

I came across this example question in my mechanics book: It's a light scale pan with negligible mass, with two blocks A and B, with masses 0.4kg and 0.6kg respectively. The pan is attached to a ...
0
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1answer
51 views

Conservation of momentum always? [closed]

Consider two atoms A and B, with A at rest and B in motion towards A. As soon as B is in the atomic field of A, will it stop with its energy going into B or will it just move up to a postion where ...
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2answers
39 views

Calculating time using SUVAT equations with unknown initial velocity

I understand that the equation used to find the equation used to find displacement when the initial velocity is unknown is: $vt-(at^2)/2$ how would you rearrange this to solve for $t\;?$ When I try ...
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0answers
29 views

How can one prove mathematically using a thought experiment that a simple pendulum will vibrate forever in an ideal condition (no friction) [duplicate]

Let's say I have a simple vibrating pendulum, if there is no friction in the space, will it vibrate forever or will it stop? How can one prove this mathematically? I tried but failed, can somebody ...
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1answer
54 views

How to sensor Jerk=$d^3{\bf r}/dt^3$, or higher derivatives (4th, 5th, 6th order) when applied in the equation of motion of a ballistic missile?

Given a 6th order differential equation of motion as usually used in ballastic missile dynamic models. What kind of sensors are usually used to measure Jerk, (or higher order derivatives in ...
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1answer
27 views

Relative velocity

Question is from Barron's SAT subject test Physics "A flat railroad car is moving to the right at 5m/s. A person standing on the car throws a ball straight upward at 20m/s. If air resistance is ...
23
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2answers
1k views

Why do most office chairs have 5 wheels?

(Inspired by Why are four legged chairs so common?) I've been wondering for a while... Why do most wheeled office chairs have 5 wheels? My guess would be that while stability vs. simplicity ...
1
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1answer
32 views

Conditions which guarantee that two points do not collide?

Consider two material points $A$ and $B$, with $B$ following $A$, moving with linear motion at constant speed and with $v_A<v_B$ (which means that, excluding possible decelerations, $B$ and $A$ ...
4
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2answers
161 views

How do the postulates of relativity relate Lorentz transforms to their inverses?

This question is about one of the assumptions involved when one is deriving the Lorentz transformation, for example under "Principle of Relativity" in Wikipedia's page on the derivations. Let me ...
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1answer
52 views

Given a current velocity and a fixed input energy, how much faster will a relativistic particle be?

The relativistic kinetic energy of a particle with mass $m$ and velocity $v_0$ is $$m c^2 (\gamma_0 - 1) \textrm{ where } \gamma_0 = \frac{1}{\sqrt{1 - \frac{v_0^2}{c^2}}}$$ I would like to know how ...
1
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0answers
38 views

Needed acceleration input to reach a target point

I have a point mass traveling on a 2D plane with some initial velocity v and initial position r. The point mass is able to ...
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0answers
66 views

Two trains collision problem [closed]

Consider two trains $A$ and $B$ travelling on a line one towards the other at speed $v_A=v_B=90km/h=25m/s$. When they are $511m$ apart the driver $A$ start braking with deceleration ...
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1answer
36 views

Tunnel through center of the earth, how to find period using $ adx=vdv$?

Suppose the boulder enters a tunnel dug through the center of the Earth along a diameter starting at rest. How would one calculate the time it takes for the boulder to reach the other end of the ...
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1answer
32 views

Methods to use in problems with equations of motion, where is required to determine a particular acceleration

I've a doubt on problems with manipulation of equations of motion. I'll make an example of a situation I'm confused about. Let $A$ and $B$ be two points that move on a line with constant speed, ...
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1answer
77 views

Position from velocity time graph [closed]

I have taken Calculus before but unfortunately no equation is given so I have to do it the old way. An object is at x = 0 at t = 0 and moves along the x axis according to the velocity-time graph ...
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0answers
34 views

Low kenitic Energy and High Kinetic Energy Atoms Attract

Will atoms of 2 difrent energy levels electron and/or Kinetic attract more than 2 Atoms at he same energy level? Do 2 high energy level atoms attract more than 2 low energy atoms?
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0answers
71 views

Equation of motion of a free particle

We know that the equation of motion of particle can be derived from the respective action. But in the book I am reading, the author is saying: ... timelike worldline of a massive particle is ...