What is Motion: Definition and 1000 Discussions

In physics, motion is the phenomenon in which an object changes its position over time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed, and time. The motion of a body is observed by attaching a frame of reference to an observer and measuring the change in position of the body relative to that frame with change in time. The branch of physics describing the motion of objects without reference to its cause is kinematics; the branch studying forces and their effect on motion is dynamics.
If an object is not changing relatively to a given frame of reference, the object is said to be at rest, motionless, immobile, stationary, or to have a constant or time-invariant position with reference to its surroundings. As there is no absolute frame of reference, absolute motion cannot be determined. Thus, everything in the universe can be considered to be in motion.Motion applies to various physical systems: to objects, bodies, matter particles, matter fields, radiation, radiation fields, radiation particles, curvature, and space-time. One can also speak of motion of images, shapes, and boundaries. So, the term motion, in general, signifies a continuous change in the positions or configuration of a physical system in space. For example, one can talk about the motion of a wave or about the motion of a quantum particle, where the configuration consists of probabilities of occupying specific positions.
The main quantity that measures the motion of a body is momentum. An object's momentum increases with the object's mass and with its velocity. The total momentum of all objects in an isolated system (one not affected by external forces) does not change with time, as described by the law of conservation of momentum. An object's motion, and thus its momentum, cannot change unless a force acts on the body.

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  1. Z

    Vibrations: A momentum impulse starts a mass into oscillatory motion

    The fig. 1.1(a) is a mass m attached to a spring that is fixed to a wall. I don't understand what does "a sudden momentum impulse" means. Is it an external force o what? I imagined that the new equation of motion would be md^2x/dt^2+dp1/dt-kx=0 md^2x/dt^2+mdv1/dt-kx=0 is this the equation i...
  2. M

    How to find the velocity of a wave in simple harmonic motion given time

    The graph provided is below. The problem asks for the speed of the wave at 0.12s. I used the formula v=w*xmax*cos(wt), provided in our textbook where xmax is the amplitude of 2 cm, w (omega) is 2pi divided by the period of 0.2. However, for some reason this formula doesn't give me the correct...
  3. C

    Projectile Motion Distance Calculation

    This based on velocity being constant. Define x0 and y0 to be zero and solve for the desired quantities.
  4. S

    How can I minimize uncertainty in circular motion experiments?

    Random error would be to do with not swinging the bung in a perfect circle so when I try to measure velocity, that would vary. Measurement of radius. How would I decrease percentage uncertainty? Use a smaller mass so that I get a larger radius so I can measure a longer length.
  5. Terrycho

    The Potential Energy Function in Three-Dimensional Motion

    I set the location of the particle (x,y,z); therefore, → the force F_1 is (z^2/root(x^2+y^2) * x/root(x^2+y^2) , z^2/root(x^2+y^2) * y/root(x^2+y^2), 0), since cosΘ is x/root(x^2+y^2). →...
  6. FahdEl

    Equation of motion using Runge-kutta 4 and Verlet algorithm

    import numpy as np import matplotlib.pyplot as plt G=6.67408e-11 M=1.989e30 m=5.972e24 X0=-147095000000 Y0=0 VX0=0 VY0=-30300 T=365*24*60 def rk(ax,ay,x,y,vx,vy,h): t=0 n=int(T/h) A=[[t],[x],[y],[vx],[vy]] for i in range(1,n): k1x=vx k1y=vy q1x=ax(x,y)...
  7. C

    Relativity - energies of particles in circular motion

    Summary: What is energy of proton, deuteron and alpha particle in circular motion of the same radius. Hello, I have a problem. Here is the content of an exercise: In some experiment, proton with energy of 1MeV is in circular motion in isotropic magnetic field. What energies would have...
  8. NP04

    Simple Harmonic Motion Experiment Problem

    I think you could try to solve for the forces based on when the spring falls from an incline at various angles theta, but I am not sure. Or spring potential energy? I'm really confused. Is there any other method? Could it involve using water and wave harmonics? (We learned waves and sound...
  9. D

    Simple Harmonic motion of a Pendulum

    First, I decided to solve for the coefficient in front of the cosine simple harmonic function for velocity. I know there is max velocity of 30cm/s at time = 0 , so I plug it into velocity function. xmax * w = A v(t) = Acos(wt) 0.3 = Acos(w*0) A = 0.3 Then I have my velocity function...
  10. gibberingmouther

    Relative Motion of Charges Question

    This problem seems pretty simple but I don't understand how the correct answer is 500,000 smaller than what I calculated. You have an electric field that has a magnitude of 10^6 V/m in the positive z direction. I assumed (though it was not stated) that the cause of this field was a sheet of...
  11. solarmidnightrose

    Is this Simple Harmonic Motion?

    I've been going to the theme park almost every year-and this year in my Physics class we are learning mechanics, more specifically Simple Harmonic Motion. My teacher told us that for an object to have 'Simple Harmonic Motion' it must have oscillatory motion (like a pendulum going back and...
  12. emarie

    Calculate the magnitude of the velocity at point from a given equation, a(t)

    These questions keep appearing in my past-papers and yet at no point in the course notes can I find a worked solution. Unfortunately I'm not sure where to start. My initial thoughts were regarding getting an equation using known values but w.r.t. to t and integrating for v, but like I said I...
  13. G

    Understanding forced motion in space

    Hello, Can you please explain the analogy oft quoted to explain the concept of applied motion to objects in space, which goes as follows : 1. You are standing on a skateboard or sitting in a boat floating on the water, holding a bowling ball. 2. You throw the bowling ball towards the back of...
  14. TheQuestionGuy14

    B Does Time Exist Without Motion?

    Is time dependent on the motion of everything in the universe? If all motion was played in reverse, so particles gain kinetic energy from sound and heat energy as they move the opposite direction, and light retreats into the sun, would time technically now be flowing backwards? If all matter (so...
  15. R

    Rotational Circular Motion with fixed ends and a spinning button in the middle

    This button has fixed ends and the string is twirled and on the fixed ends there is hanging masses. I have found out that if string twirls are constant, the hanging mass is directly proportional to angular velocity squared. But I want to understand how that is derived. Could anyone please help...
  16. M

    Writing the Equations of motion

    I have attached the problem and I have also taken a photo of my working for it, it seems my answer is wrong. I would be grateful if you could please check where I have gone wrong. Thanks a lot.
  17. W

    Geodesics and Motion in an EM Field

    I've also attached my attempt as a pdf file. My main issue seems to be I only get one A partial term. Any help would be appreciated.
  18. M

    Simple harmonic motion of a bar pivoted at one end

    Hi, I am unsure how to proceed with this problem. I believe that I can correctly calculate the frequency of the oscillations for a bar that is not suspended from a spring but I do not know how to take the effect of the spring into account. The answer given by my professor is $$...
  19. O

    Looking for an app to demonstrate motion via multiple exposure images

    I am introducing uniform and accelerated motion in a 6th grade. To demonstrate the difference I would like to use multiple exposure photography (like in the image below) in the classroom. There are many apps to make serial shoots and other apps to overlay them artfully. I am looking for an App...
  20. bigbosswilly

    High school Physics - Simple Harmonic Motion

    I started off by finding when Fg=Fx: (72)(x)=(31)(9.8) x=4.2193m After this I'm stuck and have a few things I'm confused about: When the penguin's jumping, is there elastic energy? (because the rope's getting compressed? Or maybe not). Also, I know you can use energy conservation, but...
  21. sweet springs

    I Transverse inertial motion of rockets in acceleration

    Hello. I have a question on inertial motion transverse to gravity force, e.g. blocks of dry ice floating on the smooth and flat floor on Earth. For simple mathematics I explain my problem in Rindler case. Let a group of N rockets gather at origin (0,0,0,0) of a IFR and let them start...
  22. S

    Finding equations of motion of multi degree freedom system

  23. Terrycho

    Rectilinear motion, not uniform accleration

    The photo above is the problem I'm struggling now and the photo below is what I have done so far. By differentiating and integrating the given equation, which is F=-b exp(αv), I tried to express v(t) or a(t) as a function related to t, which is time. But the more I did, the more complicated...
  24. Lunct

    Is Brownian Motion actually random or does it follow determinism?

    If you have enough information could you not determine with certainty the movements of pollen particles in water? In other words, if you were able to measure the movements the particles, then repeat the exact same experiment, with all things controlled, would the particles move in the same way...
  25. Badgun

    Impact of several variables on resulting projectile motion trajectory

    I was told to generate these variables (m, C, alpha, wind velocity) normally distributed and compare the random data with the result and then tell, which of the variables has the most impact. Here I am stuck, tried to compare variances, kurtosis and skewness of the data (the original variables...
  26. Mason Smith

    Lagrangian and Equations of Motion for Conical Pendulum

    Here is a picture of the problem. I have chosen the origin to lie in the middle of the circle around which the mass moves. I have also chosen the z axis to pass through the origin and through the vertex of the right circular cone. The x-axis and y-axis are so that one when curls his or her...
  27. J

    Why Does a Spinning Object Wobble but Not Tumble?

    When you spin a bowl, for instance, and it wobbles as it spins in circles. I've always been captivated at this motion, and have never been able to find the name for it. Sounds silly, but I think there's an un-tapped (as far as I know) force at work there. Thoughts? BTW, I'm definitely not in HS...
  28. F

    Calculating Centripetal Acceleration in a Vertical Loop

    $$mg(0.45) = mg(R + R \cdot cos(\frac{π}{3})) + \frac{1}{2}mv^2$$ $$v^2 = g(0.9 - 3R)$$ The centripetal acceleration during the "flying through air" will be given by gravity $$mg \cdot cos(\frac{\pi}{3}) = \frac{mv^2}{r}$$ $$R = \frac{1.8}{5}$$ But my book says $$ R = \frac{1}{5}$$
  29. S

    Solving Particle Motion in a Rigid Box: t=0

    I have question, how can I solve problem of particle in rigid box when one of the wall gets completely destroyed? At time t = 0 the right wall of box gets completely destroyed, left wall is still here( ψ(0) = 0 ), also at t = 0 we know that particle is in ground state. How can I search for...
  30. babaliaris

    Uniform Circular Motion: some help with the math proof?

    I can not understand why ##v_x = -|v|sin(θ)## and ##v_y = |v|cos(θ)## I'm asking about the θ angle. If i move the vector v with my mind to the origin i get that the angle between x'x and the vector in anti clock wise, it's 90+θ not just θ. So why is he using just θ? Does the minus in v_x somehow...
  31. babaliaris

    Projectile Motion: Path's length?

    So I just learned about projectile motion. I understand why you can study it as two independent straight line motions . But this can give you a way to calculate total velocities or accelerations, just by adding its individual component of each vector. If the initial position of the projectile...
  32. E

    Projectile Motion Experimental Error

    Homework Statement I got an experimental vertical acceleration of -12 m/s^2 of projectile motion for an experiment I did at home where I just had to throw a ball at around 45 degree to the horizontal up in the air and record it's motion, then analyze the motion via computer software. Obviously...
  33. Ariano AnnaG

    Circular motion of a rotational spring

    Homework Statement A child is playing with a spring (k=100000 N/m, Li = 0.5 m). One of his toys (m=0.5 kg) is attached to the further extremity. The child is rotating the spring above his head on a horizontal plane, with a uniform circular motion. What is the elongation of the spring? I’m not...
  34. EEristavi

    Motion in 2 Dimensions & Relative velocity

    Homework Statement The water in a river flows uniformly at a constant speed of 2.50 m/s between parallel banks 80.0 m apart. You are to deliver a package across the river, but you can swim only at 1.50 m/s. (c) If you choose to minimize the distance downstream that the river carries you, in...
  35. L

    I Equation of motion Chern-Simons

    The Lagrangian (Maxwell Chern-Simons in Zee QFT Nutshell, p.318) has as equation of motion: Where does the 2 in front come from? Thank you very much
  36. F

    Motion Homework -- A particle moving along the x-axis....

    Homework Statement The position function x(t) of a particle moving along an x axis is x = 6.00 - 7.00t2, with x in meters and t in seconds. Homework Equations (a)[/B] At what time and (b) where does the particle (momentarily) stop? At what (c) negative time and (d) positive time does the...
  37. R

    Finding the period of the satellite's orbital motion

    Homework Statement I want to find the period of the satellite. Homework Equations mg = mv^2/r The Attempt at a Solution I derive the equation mg = mv^2/r v = sqrt(gr) v = ωr and ω = 2π/T T = 2π/ω = 2πr/v Then, T = 2πr/sqrt(gr) But the answer is 2πr/R * sqrt(r/g). I don't know why? Is...
  38. solzonmars

    Solve Cyclotron Motion Homework

    Homework Statement An electron in a cathode-ray tube is accelerated through a potential difference of 10 kV, then passes through the d = 2.4-cm-wide region of uniform magnetic field in the figure. Homework Equations - Am I taking the entirely wrong approach in the solution? The Attempt at a...
  39. E

    Projectile Motion with Pulley System

    Homework Statement The pulley device is used to hurl projectiles from a ramp (Coefficient of Kinetic friction [mu] = 0.26) as illustrated in the diagram. The 5.0 kg mass is accelerated from rest at the bottom of the 4.0 m long ramp by a falling 20.0 kg mass suspended over a friction less...
  40. Celso

    Simple harmonic motion interpretation problem

    I'm in trouble trying to understand the expression ##t= \frac{1}{\omega} cos^{-1}(x/A)## that comes from ##x = Acos(\omega t)##, in which ##A## is the amplitude, ##t## is time and ##x## is displacement. When ##x = 0##, ##t = \frac{\pi}{2\omega} ##, shouldn't it be 0 since there was no movement?
  41. D

    Equation of motion for oscillations about a stable orbit

    Homework Statement A) By examining the effective potential energy find the radius at which a planet with angular momentum L can orbit the sun in a circular orbit with fixed r (I have done this already) B) Show that the orbit is stable in the sense that a small radial nudge will cause only...
  42. N

    Using first principles, how to get the equation of motion?

    << Mentor Note -- thread moved from the technical forums, so no Template is shown >> Show, from the first principles, that the equation of motion of a mass (m) on a spring, subjected to a linear resistance force R, a restoring force S, and a driving force G(t) is given by d2x/dt2+ 2K(dx/dt) +...
  43. Mert Kerem Yavuz

    Motion of a system that has two masses and three pulleys

    Homework Statement Homework Equations F = ma The Attempt at a Solution I couldn't draw the freebody diagram. There's this weight of mass m, which is mg, downwards from m and there's tension T to upwards. This T affects mass M in the +x direction, but how could i find out the normal force...
  44. R

    Projectile motion -- Maximum range it can travel inside a 2m tunnel

    Homework Statement A particle is projected inside a tunnel which is 2 m high and must not hit the side or ceiling of the tunnel. If the initial speed is U show that the maximum range of the particle inside the tunnel You may assume that the maximum range is attained when the projectile just...
  45. A

    B For Lack of a Better Term....Moon Motion

    It has often been posed that one reason humans cannot feel the motion of the Earth as it spins and moves around the Sun is that our bodies have acclimated to this motion due the fact that it is all we have ever known. If true, does this mean that astronauts have experienced feeling the motion...
  46. G

    Request about experiments on the linear-motion Faraday paradox

    The Faraday paradox is a very curious example in the topic of relative motion. An experiment demonstrating the curious results is shown in the video below: This has made me curious about the linear version of the Faraday paradox. A conductor placed atop a magnet, both at rest in one scenario...
  47. Abhishek11235

    Can Lagrangian Method be Applied to Solve Rocket Motion Equations?

    Homework Statement While solving equation of rocket motion with Newton's law in 1-d,I pondered to apply Lagrangian method on this. However, I didn't get correct result. Because I can eliminate last 2nd equation using last equation and get some other equation which is certainly not rockets...
  48. S

    You're welcome! Good luck with your project.

    First time poster here, thanks in advance! I have a project I'm working on, and I'm looking for a way to limit the rotational motion of a shaft inside a cylinder. The cylinder is fixed, and the shaft is spinning inside the cylinder coaxially. Basically, torque will be applied to the shaft...
  49. Hoophy

    Circular Motion With Constant Angular Acceleration

    Homework Statement Question: A 600 g steel block rotates on a steel table while attached to a 1.20 m-long hollow tube. Compressed air fed through the tube and ejected from a nozzle on the back of the block exerts a thrust force of 5.01 N perpendicular to the tube. The maximum tension the tube...
  50. Hoophy

    Uniform Circular Motion, Find the Tension

    IMPORTANT! TEXT IN GREEN HAS BEEN ADDED AND IS CORRECT TEXT IN RED HAS BEEN REMOVED AND IS INCORRECT 1. Homework Statement Question: An energetic father stands at the summit of a conical hill as he spins his 25 kg child around on a 5.7 kg cart with a 2.3-m-long rope. The sides of the hill are...
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