What is Kinematic: Definition and 406 Discussions

Kinematics is a subfield of physics, developed in classical mechanics, that describes the motion of points, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause them to move. Kinematics, as a field of study, is often referred to as the "geometry of motion" and is occasionally seen as a branch of mathematics. A kinematics problem begins by describing the geometry of the system and declaring the initial conditions of any known values of position, velocity and/or acceleration of points within the system. Then, using arguments from geometry, the position, velocity and acceleration of any unknown parts of the system can be determined. The study of how forces act on bodies falls within kinetics, not kinematics. For further details, see analytical dynamics.
Kinematics is used in astrophysics to describe the motion of celestial bodies and collections of such bodies. In mechanical engineering, robotics, and biomechanics kinematics is used to describe the motion of systems composed of joined parts (multi-link systems) such as an engine, a robotic arm or the human skeleton.
Geometric transformations, also called rigid transformations, are used to describe the movement of components in a mechanical system, simplifying the derivation of the equations of motion. They are also central to dynamic analysis.
Kinematic analysis is the process of measuring the kinematic quantities used to describe motion. In engineering, for instance, kinematic analysis may be used to find the range of movement for a given mechanism and working in reverse, using kinematic synthesis to design a mechanism for a desired range of motion. In addition, kinematics applies algebraic geometry to the study of the mechanical advantage of a mechanical system or mechanism.

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  1. T

    Calculate the kinematic threshold energy of a proton

    Homework Statement Given the reactions: p + 9 Be --> 10B + "gamma" p + 9 Be --> 9B + 1n p + 9 Be --> 9Be + 1p p + 9 Be --> 8Be + 2H p + 9 Be --> 7Be + 3H p + 9 Be --> 6Li + 4He Calculate: a) Q-value b) kinematic threshold energy of the proton...
  2. A

    Kinematic Description of Stewart Platform

    This question is about a multibody kinematic describtion of a Stweart Platform. We are doing some experiments with a Stewart platform, which is a six-legged parallel manipulator and is well described in literature. You see this robot in my top figure. For the first situation I want to find a...
  3. G

    Kinematic equation for 4-bar linkage

    Looking For Help to derive the kinematic equation for the 4-bar linkage shown; (to find the angular position of the cylinder at different values of theta )
  4. B

    Rearranging the kinematic equations

    The equations for linear motion I've memorized are: 1.) v = u + at 2.) v^2 = u^2 + 2as 3.) s = ut + 1/2(at^2) v = final velocity, u = initial velocity, a = acceleration, t = time, s = displacement In an example my physics teacher uses the equation x = x0 + (v^2-u^2)/2a I'm assuming he...
  5. G

    Rotational / Linear kinematic problem

    Homework Statement http://img691.imageshack.us/img691/2702/drawing1.png A 1kg block is suspended from a rope that wraps around a pulley where it is pulled by a 10N force. The pulley is a disk with mass 50g and has a diameter of 4cm. Assume enough friction that the rope does not slip but...
  6. D

    How Do You Calculate Stopping Time and Deceleration for a Car?

    Homework Statement A car is traveling along a highway with a speed of 25m/s when the driver sees an obstruction 180m directly ahead. It takes the driver 0.80s to react and begin breaking. A) How long will it take the car to stop once brakes are applies, provided the car stops just before...
  7. M

    Kinematic equations - What do they mean?

    I'm in a physics 201 course and very confused about the kinematic equations. Is there anybody out there who can describe what each one means? Thanks, Mike
  8. C

    How far will a car travel before coming to rest?

    A car is decelerating uniformly. Its velocity changes from 30m/s to 15m/s in 75m. How much further will it travel before it comes to rest? - Please, i need a detail answer. Thanks!
  9. T

    Is the Kinematics of 3D Space Truss Affected by Closed Loops in the System?

    Hi, I am a PhD student in math and in my current research I'm faced with the problem of analyzing the rigidity of a structure of rigid beams in 3D, that is if the structure can move. In particular, something like this: http://img525.imageshack.us/img525/1545/98322092.th.jpg where all...
  10. S

    How Long Until the Second Car Overtakes the First?

    Homework Statement A car starts from rest and accelerates uniformly at 3 m/s2. A second car starts from rest 6 s later at the same point and accelerates uniformly at 5 m/s2. How long does it take the second car to overtake the first car? How would I solve this? If someone can break it down...
  11. S

    Easy kinematic problem I've suffered an hour for

    Homework Statement Metal ball is launch at 30 degrees from initial height of 1m with initial speed as 7.66m/s, find horizontal distance traveled Homework Equations The Attempt at a Solution Honestly I have no idea.
  12. S

    Kinematic Problem: Finding Initial Height of a Thrown Baseball in 2.53 Seconds

    Homework Statement Baseball is throwing upwards with initial velocity as 12m/s. Total time it took to reach ground is 2.53 seconds. Find the initial height where baseball was thrown. Homework Equations The Attempt at a Solution Find d t=2.53 Vo=12 0=d+Vo*t-4.9t^2 0=d+12*2.53-4.9t^2...
  13. K

    Need help finding Kinematic formula for Initial V

    Homework Statement A truck covers 60.0 m in 9.0s while smoothly slowing down to final speed 3.00 m/s. Find the initial velocity. Homework Equations Vi +1/2at^2 has two unknowns V= vo + at has two unknowns x= v^2 - Vi^2/2a has two unknowns v^2=vi^2 +2a(xf-xi) has two unknowns...
  14. C

    Falling object 1D Kinematic Question

    Homework Statement An object falls from height h from rest. If it travels .5h in the last second before hitting the ground, determine how long it takes to fall and the height h. xi = .5hm, t =1s, a = 9.8m/s^2, xf = 0m, Homework Equations Vf = Vi + at xf = xi + .5at^2 The Attempt at a...
  15. J

    The Work-Energy Principle & Kinematic Eq'ns to calculate speed

    Homework Statement A spaceship of mass 5.00 x 104 kg is traveling at a speed 1.15 x 104 m/s in outer space. Except for the force generated by its own engine, no other force acts on the ship. As the engine exerts a constant force of 4.00 x 105 N, the ship moves a distance of 2.50 x 106m in...
  16. T

    Fluid Mechanics Question: Calculation of kinematic velocity

    hey guys I am new to the forum... i am a first year civil engineering student trying to do a second year course over this summer holiday. for fluid mechanics i was given this h/w problem. could you please tell me if I am correct and if not make explain where i went wrong and how to correct it...
  17. S

    Isotropic and kinematic ahrdening(metals)

    I've been trying to figure out difference between isotropic and kinematic hardening (modeling plasticity in metals). As I see,kinematic hardening can model reversible nbehaviour of metals (Bauschinger effect). In isotropic hardening, the yield surface increase in size, but remain the...
  18. M

    Kinematic Pairs & Chains: What are They?

    can someone tell me the exact definition of kinematic pairs?and kinematic chain? which is the one where relative motion is constrained?
  19. T

    Solving Kinematic Problem: Initial Velocity of a Ball

    Homework Statement Determine the initial velocity of a ball which starts 3ft above the ground travels a distance of 180ft and has an angle of 30 degrees; taking into account gravity as 32.2ft/s2. Homework Equations I have been having trouble as to how to get the time in which it takes the...
  20. N

    Equivalence of the 'expanding space' & 'kinematic' paradigms

    The Equivalence Principle suggests the possibility that a 'kinematic' paradigm might produce exactly the same cosmic observations as the standard 'expanding space' paradigm. In my view, functional equivalence demands that the 'kinematic' paradigm make the same observational predictions as the...
  21. W

    Kinematic Equations: View List & Explanations

    v = v0 + a*t x = x0 + v*t Is there a page or a website where I can view kinematic equations like this which explains them and list them all down.
  22. D

    Exploring the Depth: Solving a Kinematic Mystery in a Cave | 15m Deep

    Homework Statement An explorer drops a pebble into a cavern to see how deep it is. At 1.8 seconds, the explorer hears the pebble hit the water. The speed of sound travels at 345 m/s in the cave. How deep is the cavern? This seems like a kinematic question but I can seem to get the right...
  23. K

    Kinematic Car Race: Which Car Will Win with and without Friction?

    Homework Statement Two cars start 10 meters up a hill. Car A has a mass of 9 grams and Car B has a mass of 2 grams. Additionally, both cars must travel the same distance to the finish line. a) If friction is ignored which car will win the race? b) If friction is not...
  24. K

    Which kinematic equation should be used?

    Homework Statement My question is for concept clarification, not a problem that needs to be solved/calculated. I posted this question previously, "The velocity graph of a particle moving along the x-axis is shown. The particle has zero velocity at t=0.00 s and reaches a maximum velocity...
  25. B

    Analyzing the kinematic x(t) equation

    Homework Statement Solve the equation below for deltaX symbolically and simplify the answer as much as possible. deltaY = (tan A)deltaX - g*deltaX^2/2V(initialx)^2 Homework Equations quadratic equation. The Attempt at a Solution I can handle the algebra and simplification. My...
  26. S

    Something weird about Rotational Kinematic Equations

    Homework Statement I need to find the average acceleration of a gramophone record. Initial angular velocity, W = 0 Final angular velocity, w = 3.50rad s^-1 angular displacement, 8 = 0.25rad Homework Equations The equation given by the answer is t= 8/w a = ( w - W ) / t the answer is 49.0...
  27. R

    Understanding Kinematic Equations of Motion

    Can anyone help me familiarize myself with the Kinematic Equations of Motion? I need to know them for this summer institute. Thanks, Randeezy
  28. J

    How Can Kinematic Equations Prove Vf² Equals vi² Plus 2ad?

    Use the Kinematic Equations vf = vi + AT and D= viT + 0.5AT2 to show that Vf2 = vi2+2ad
  29. D

    Kinematic and Isotropic Hardening

    Hello, Could anyone help explain what Kinematic and Isotropic hardening are. Any brief explanation or reference to a good book that explains these topics would be very useful. Thank you
  30. D

    How Long Did the Runner Accelerate to Finish the 1500m Race on Time?

    Homework Statement A runner wants to run a 1500m race with an average velocity of 6.00m/s. After running the first 500 m, he notices that the elapsed time is 1 min 40 seconds. Panicking, he accelerates for "t" seconds at 0.20 m/s² and then finishes the race at his new faster speed. He makes...
  31. K

    Rearranging Kinematic Equations. Help.

    Homework Statement Homework Equations The Attempt at a Solution The template doesn't really apply to what I need help with. I've missed some school and I need help rearranging Kinematic equations. I am new to physics so please use plain english. Here's the specific one I am having problems...
  32. E

    One Kinematic Problem, One Pendulum Problem, One Wave Problem

    Homework Statement ok well this was my homework over the weekend and i think i got an idea of how to solve these but I am not quite sure on my answers... I've scanned the problems because they all require diagrams that must be seen to solve the problems...
  33. D

    Kinematic Problem: Tangential Acceleration and Radius of Curvature at t=1

    a body moves according to the following: ay=2-4t ax=-1 vy=2t-2t2 vx=1-t x0=2 y0=3 what is the tangential acceleration when t=1? what is the radius of curvature of the motion when t=1? aT=\vec{a}dot\vec{v}/|v| at t=1, \vec{v}=0 so there is no tangential acceleration, how can this...
  34. T

    Kinematic Equations: Position & Velocity at t=2.40s

    Homework Statement Using the appropriate kinematic equations and initial values, determine the position and velocity at t=2.40 s. (x, y)=0, 0 (vi, 0)=(25.0 m/s, 65.0 degree) a.Horizontal Velocity of the initial velocity b.Horizontal/Vertical Velocity at 2.40 s c.Horizontal...
  35. S

    Simple kinematic equations question?

    Homework Statement A 52.2 kg pole-vaulter falls from rest from a height of 3.6 m onto a foam-rubber pad. The pole-vaulter comes to rest 0.34 s after landing on the pad. (a) Calculate the athlete's velocity just before reaching the pad. (b) Calculate the constant force exerted on the...
  36. V

    Static and kinematic determinacy

    What is the difference between a structure being statically indeterminate and being kinematic? Are they the same?
  37. I

    How can I solve 1-D kinematics problems with limited resources?

    Homework Statement I have a problem worksheet for my 'Physics A' class. It deals with 1-D Kinematics, which we are just getting into so I am not very sure what equations I need to use. I'm not asking for someone to answer them for me, but to maybe give me a list of a few equations that would...
  38. P

    Understanding the kinematic equations

    So I am trying to fully understand how to come about the kinematic equations for uniformly accelerated motion. So v = dr/dt and a = dv/dt How does the math work behind this I know the second is the derivative of the first. dr = v*dt dv = a*dt So dv is the...
  39. P

    Simple physics kinematic one dimension problem?

    Homework Statement Driving along a crowded freeway, you notice that it takes a time t to go from one mile marker to the next. When you increase your speed by 5.0 mi/h, the time to go one mile decreases by 13 s. What was your original speed in mi/hr? Homework Equations X (which in...
  40. M

    How Much Farther Will Wonder Boy Hit the Baseball?

    1. You have recently been struggling when stepping up to the plate to bat. You can no longer hit for power. To combat the problem you go see Bobby the bat boy and ask him for "Wonder Boy." This bat is 1.5 inch longer than the bat you currently use. Assume that: -you can swing both bats...
  41. F

    Kinematic equations and their applications

    Hello, I have a question concerning the kinematic equations http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L6a1.gif vi and vf stand for initial and final velocity, my question is: do these velocities need to be the initial (t=0) and final (end of the motion)? can't I just...
  42. F

    Answer Check for kinematic in 2-d

    Homework Statement In a local bar, a customer slides an empty beer mug down the counter for a refill. The bartender is momentarily distracted and does not see the mug, which slides off the counter and strikes the floor 1.10 m from the base of the counter. The height of the counter is 0.820...
  43. K

    Just wondering is the solution right?it is a 1D kinematic problem

    Just wondering is the solution right?it is a 1D kinematic problem Homework Statement An elevator ascends with an upward acceleration of 1.2m/s^2. At the instant its upward speed is 2.4 m/s, a loose bolt drops from the ceiling of the elevator 2.7m from the floor. Calculate the time of flight...
  44. S

    Kinematic Question: Horizontal & Vertical Velocity Components

    Homework Statement A golfball is hit with a velocity of 25m/s at an angle of 40 degrees above the horizontal. What are the horizontal and vertical components of the velocity? i don't want the answer that's not my objective... just the correct formula cause I've been using all these...
  45. S

    Calculating Resultant Velocity of Plane: Kinematic Questions

    Homework Statement A pilot heads his airplane due east at a speed of 75 m/s. While he is flying, a wind blows at 60 degrees North East with a constant speed of 25 m/s. What is the reultant velocity of the plane? Homework Equations s=(u+v/2)t, v=u+at, and s=ut+1/2at² The Attempt at...
  46. F

    What Is the Average Acceleration of a Super Ball Bouncing Off a Wall?

    Homework Statement A 50.0 g Super Ball traveling at 28.0 m/s bounces off a brick wall and rebounds at 19.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.50 ms, what is the magnitude of the average acceleration of the ball during this time interval...
  47. M

    Solve Kinematic Problem with Friction Along Curve | Mass Included

    Please see the attached problem I came up with. I've done similar problems to this in school, but never with the frictional force acting along a curve. I'm wondering if my solution is valid, or if the integral needs some work? And I just realized I left out the mass [M] in the normal force...
  48. T

    Can gravity be a kinematic effect?

    One interesting thing in quantum mechanics is that there are correlation effects which can manifest themselves as dynamic effects, for example, as kinematics of fermions can make free electron model a good approximation for some phenomenons observed in solids, by effective cancellation of very...
  49. wolram

    Kinematic Origin of Cosmological Redshift: Bunn & Hogg

    arXiv:0808.1081 (cross-list from physics.pop-ph) [ps, pdf, other] Title: The kinematic origin of the cosmological redshift Authors: Emory F. Bunn, David W. Hogg Comments: 14 pages. Submitted to Am. J. Phys Subjects: Popular Physics (physics.pop-ph); Astrophysics (astro-ph); General...
  50. D

    Sketch a Kinematic Scheme | Help with Joints

    I am not sure if I'm in the right section to post this, but I'm going to try anyway... http://img124.imageshack.us/img124/6281/clipboard02ub1.jpg Could anybody please show me how to sketch a kinematc scheme of this structure? I don't know how to represent the joints (especially the...
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