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. L

    Skating ramp, only height given. Kinematic equations.

    Homework Statement A skater jumps off a quarterpipe ramp and reaches 5m over the ramp. We can assume that he jumps in a vertical line. Find the speed the skater had before jumping off the ramp. Homework Equations https://www.physicsforums.com/threads/introductory-physics-formulary.110015/ All...
  2. J

    Finding Velocity from only distance

    Mod note: Moved from technical section, so no template Question: The ace Edward bow can shoot 182.8 meters at a 45 degree angle, it can shoot 12 arrow per minute. What is the performance of the Bow? Attempt: Basically considering the Dx=182.8 meters I assume the Dy is the same considering its...
  3. GZM

    Complicated Kinematic problem dealing with falling

    Homework Statement Problem states : A student walks off the top of the CN Tower in Toronto, which has height h and falls freely. His initial velocity is zero. The Rocketeer arrives at the scene a time of t later and dives off the top of the tower to save the student. The Rocketeer leaves the...
  4. F

    Chain rule and Kinematic quantities x,v,a

    Hello Forum, I have a couple of kinematics questions. The position of a point object is given by the position vector x(t). Speed is v(t)=dx(t)/dt and the acceleration a(t)= dv(t)/dt. What if we wanted to know the velocity and/or the acceleration as a function of position, i.e v(x) or a(x)...
  5. L

    What is the definition of the degrees of freedom in a kinematic chain?

    As I know, when a link in a kinematic chain is fixed, the kinematic chain will become a mechanism. And, I only know the definition of the DOF of a mechanism. Is there the definition of the DOF of a kinematic chain ?
  6. L

    Girl running after a bus, kinematic equations.

    Homework Statement Marie is running to catch a bus. The bus has stopped at a bus stop. The bus has the acceleration 0.75m/s^2. Marie has the speed 8m/s. Before the bus starts driving, the space between Marie and the bus is 17.5m. A How long will it take for Marie to catch up to the bus? B What...
  7. M

    Calculating the Depth of a Well and Velocity of a Rock Using Equations of Motion

    1. A rock is dropped into a well of an unknown depth. 20 seconds after the rock is dropped the splash is heard at the top of the well. What is the depth of the well? What is the velocity of the rock when it reached the bottom?2. X= Xo + Vo(t) + 0.5(a)(t^2) V= Vo + a(t) (V^2)= (Vo^2) + 2a(X-Xo)...
  8. L

    How Long Until the Arrow Hits the Rock in Helm's Deep?

    Homework Statement Picture yourself in the castle of Helm's Deep from the Lord of the Rings. You are on top of the castle wall and are dropping rocks on assorted monsters that are 19.10 m below you. Just when you release a rock, an archer located exactly below you shoots an arrow straight up...
  9. Mr Davis 97

    Simple kinematics question -- dropping a stone down a well

    Homework Statement [/B] A boy drops a 0.10 kg stone down a 150 m well and listens for the echo. If the speed of sound is 343 degrees Celsius, the how long after the stone is dropped will the boy hear the echo? Homework Equations v = d/t v2 = v2 + 2ax The Attempt at a Solution [/B] What I...
  10. Deep Dhillon

    Approaching a Cops and Robbers Chase Problem Using Equations of Motion

    Homework Statement A cops and robbers chase is set up as follows 1. Both the police car and the robber's can start from rest 2. The robbers have 1 km head start 3. The robber's van accelerate at 0.50 m/s 4. The police car accelerate at 0.60 m/s Use famous 5 equations to answer the...
  11. N

    Rotational kinematic need explanation

    ice skater with mass = 80 kg moment of inertia (about her central axis) 3 kg m2. Catch baseball with outstretched arm 1m from her central axis. Ball has mass 0.3 kg and v0 = 20 m/s before the catch. V system ( skater + ball ) after catch = 0.0747 m/s Question : b. Angular speed of the...
  12. C

    Calculating initial velocity using kinematic equations

    Hi! I'm working on a problem for class and am having trouble figuring out how to calculate the initial velocity, which I need in order to calculate acceleration and from there the value of an unknown force. I thought I was on the right track, but my professor reminded me that I need to use the...
  13. red1312

    Calculating Horizontal Distance for a Falling Object Without an Angle

    Homework Statement A girl shoves a book at rest on a table and it moves with an acceleration of 1.3 m/s . After 5 s, the book falls at the edge of the table. If the table height is 1.2 m, find the horizontal distance that it hit the floor. (ans: 3.22 m) ... How the answer would be 3.22...
  14. H

    A=F/M Based problem - air track glider

    At time t=0 s a 0.362-kg air track glider is moving rightward at 5.1 m/s. At t=2.5 s, it's going leftward at 5.4 m/s. Determine the magnitude and direction of the constant force that acted on the glider during this interval. Give your answer in Newtons. If the force is going rightward, your...
  15. Elvis 123456789

    Projectile Motion balloon question

    Homework Statement A 124-kg balloon carrying a 22-kg basket is descending with a constant downward velocity of 23.5m/s A 1.0-kg stone is thrown from the basket with an initial velocity of 14.8m/s perpendicular to the path of the descending balloon, as measured relative to a person at rest in...
  16. MidgetDwarf

    Help with simple kinematic problem

    A fast food restaurant uses a conveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor travel? If the burgers are spaced 15 cm apart, what is the rate of of burger production (in...
  17. J

    Distance to traveled to reach 0m/s not matter in impulse?

    Homework Statement I figured out this homework problem, after many tries, but I'm confused about the correct final answer. Here's the question: The rebounding ball, mass of 0.06 kg, traveling horizontally at 7.6 m/s, is caught by a player who brings it to rest. During the process, her hand...
  18. R

    Max Reaction Time to Avoid Obstacle 95m Away

    Homework Statement a vehicle is traveling at 25m/s. its breaks provide an acceleration of -3.75m/s^2. What is the drivers maximum reaction time is she is to avoid hitting an obstacle 95.0m away? Homework Equations D=vi(t) +1/2a(t)^2 3. The Attempt at a Solution D=95m vi=25 m/s a=-3.75m/s ^2...
  19. Diego Fernandez

    Can an Object Have Acceleration at Zero Velocity?

    Homework Statement I'm taking my first basic physics course and I came across this simple question (which I got the wrong answer apparently). The question was this: what is the velocity and acceleration of an object which has reached it's maximum height after being thrown directly upwards...
  20. S

    Lagrange mechanics: Pendulum attached to a massless support

    Homework Statement A simple pendulum of length ##b## and bob with mass ##m## is attached to a massless support moving vertically upward with constant acceleration ##a##. Determine (a) the equations of motion and (b) the period for small oscillations. 2. Formulas ##U = mgh## ##T = (1/2)mv^2...
  21. S

    Lagrangian mechanics: sphere inside a cylinder

    The problem goes by this: A sphere of radius ##\rho## is constrained to roll without slipping on the lower half of the inner surface of a hollow cylinder of inside radius R. Determine the Lagrangian function, the equation of constraint, and Lagrange's equations of motion. Find the frequency of...
  22. M

    Parity as a kinematic property?

    Weird question, but does anyone have any feelings on whether parity can be classified as a kinematic property? It doesn't scale with energy and so in that sense doesn't seem to be classifiable as a dynamic property, nor do objects interact through it; but parity is of course violated by the...
  23. D

    Kinematics Question. Incline, Spring, Friction

    Homework Statement Practice problem for midterm. Homework Equations [/B] T_1+U_1=T_2+U_2 U_spring=1/2kx^2The Attempt at a Solution [/B] Set X-axis along the 30 degree line and the Y-axis perpendicular. I'm not sure how to consider the friction constant into the formula. Any help is very...
  24. R

    Calculating Kinetic Friction for Skidding Motorcycle

    Homework Statement A biker and his motorcycle have a weight of 2350 N [down]. Calculate the force of kinetic friction for the rubber tires and dry concrete if the motorcycle skids. (Coefficient of friction is 0.7) Homework EquationsThe Attempt at a Solution my answer i got was 1645 but the...
  25. P

    Kinematic Problem: MJ & SP Meet - Find Distance

    Homework Statement MJ falls from rest from a tall building. 1.5 seconds later SP throws himself downward with an initial velocity of -45 meters per second. Find the distance where they meet. variables: α1= -9.81 α2=-9.81 Δγ1 = ? Δγ2=? Δ†1=? Δ†2=? + 1.5 ∨i1=0...
  26. L

    Kinematic Equations Used to Find A.) Average Speed & B.)Acceleration

    Homework Statement A truck covers 40.0m in 7.15 s while uniformly slowing down to a final velocity of 3.50 m/s. a.) Find the truck's original speed b.) Find it's acceleration Homework Equations Δx = Vav(Δt) = (V+Vo/2)Δt a=(V-Vo)/(Δt) The Attempt at a Solution Part A.)...
  27. C

    A projectile kinematic in 2 d problem using baskeballs?

    Homework Statement A basketball leaves a player's hands at a height of 2.20m above the floor. The basket is 3.05m above the floor. The player likes to shoot the ball at a 35.0∘ angle.If the shot is made from a horizontal distance of 5.90m and must be accurate to ±0.22m (horizontally), what...
  28. V

    Kinematic Problem: Bullet vs. Block Falling Speed Explained

    Homework Statement A large very powerful gun shoots a bullet that easily goes through a block. In the process the block is knocked off the post and falls to the ground. Which hits the ground first, the bullet or the block. Why? Homework Equations The Attempt at a Solution I am...
  29. L

    Advanced One Dimensional Kinematic Problem

    A car is traveling at 25 m/s when it runs off the road and hits a utility pole. The car stops instantly, but the driver continues to move forward at 25 m/s. The airbag starts from rest with a constant acceleration from a distance of 50 cm away from the driver and makes contact with him in 9...
  30. D

    Kinematic Equation Problem using Velocity & Distance

    Hey guys, I'm confused on this problem: It is a typical sunny day. Assume your reaction time is 0.50 s and the acceleration of your car is –8.2 m/s2. What is the no-skid stopping distance when the car’s speed is initially 26.9 m/s? Homework Statement a=-8.2 m/s^2 v0=26.9 m/s v=0...
  31. A

    Kinematic -- If object in 5th and 6th sec passes 20

    Homework Statement Object from state of inaction starts to move with equal acceleration. If objec in 5th and 6th sec passes 20, what's acceleration. Homework Equations s=v0*t+a*t*t/2 v0=0 The Attempt at a Solution s=a*t*t/2 a=s/2 a=10
  32. L

    MHB Understanding Kinematic Relative Motion: Solving Problem 1

    HElp With Problem 1 see image Ahora In THIS problem Part 1 without wind I understand it perfectly But where are the 10 km and 20 km come from? y b) Why do arcsin ( 40/220)?
  33. J

    Kinematic time dilation in black holes

    Black hole A moves at slow velocity, and there's an Einstein light clock hovering near the event horizon. Black hole B moves at high velocity, and there's an Einstein light clock hovering near the event horizon. The black holes are identical. And the light clocks are at the same...
  34. K

    Finding the location of a kinematic particle in motion based on time.

    Hello there, I have a problem that I've been trying to solve for some time now and I find myself struggling. I am trying to develop a method of calculating the position of a particle using kinematic motion in a 2D Cartesian coordinates system given a set of starting values based on how much...
  35. B

    Solving for Time of Intersection in Vertical Kinematic Problem

    Homework Statement A stone is dropped of a cliff. A second stone is thrown down the cliff at 10 m/s at 0.5s after the first stone. When do the stones cross paths? Homework Equations Yf = vt + at^2/2 The Attempt at a Solution My logic is the set the final position Yf equal for both stones...
  36. marellasunny

    Kinematic analysis:Application of defining path of joint

    I understand that defining the path of a joint in a mechanism comes under the category of 'kinematic analysis'. I do not understand why engineers do this,when all they need to know is the path of the piston,piston velocity and piston acceleration(kinematic analysis). Take for example this 90...
  37. J

    Vectorial kinematic in cartesian and polar system/notanion

    I was trying to study vectorial kinematics in all its fullness, without decorating formulas, only deducting all vectorially through mathematical definitions. I felt much difficulty, because it's a puzzle of many pieces and I not found a embracing explanation in any book. Someone could explain to...
  38. S

    Kinematic Equations for Projectile Motion

    Homework Statement How long will an arrow be in flight if it is shot at an angle of 25 degrees above the horizontal and hits a target 50.0m away at the same elevation? Known: displacement in x-axis: 50.0m acceleration in x-axis: 0m/s2 displacement in y-axis: 0m acceleration in y-axis...
  39. J

    Skiing both ways conservation of energy/1D kinematic

    skiing both ways...conservation of energy/1D kinematic Homework Statement A skier starts from rest at the top of a 45.0-m-high hill, skis down a 30° incline into a valley, and continues up a 40.0-m-high hill. The heights of both hills are measured from the valley floor. Assume that friction...
  40. P

    How Do You Calculate Minimum Constant Acceleration for a Jumbo Jet Takeoff?

    I'm confuse by what the question is asking as far as the conversion (km/hr/s). Can any please help me? Homework Statement A jumbo jet must reach a speed of 240 km/hr on the runway for takeoff. What is the minimum constant acceleration (in km/hr/s) needed for takeoff from a 1.34 km runway...
  41. B

    Solve Kinematic Equations for Collision of Carts

    Hey guys how's it going. My physics teacher gave us a challenge problem for extra credit, me needed the extra credit i decided to come here for help. Homework Statement here is the link to the problem itself. http://www.modelingphysics.org/consta/challenge.pdf I have actually done number...
  42. H

    Mastering the 5 Kinematic Equations: An In-Depth Look at Motion Rules

    I know that there's 5 key equations for motion which is: d = (vf+vi/2)t vf = vi + at d = vit + 1/2at^2 vf^2 = vi^2 + 2ad d = vft - 1/2at^2 Correct? But my teacher was confusing me today and he taught us these two other equations: d = 1/2(vi+vf)t d = 1/2at^2 What are...
  43. J

    Car Traveling the Circle - Kinematic Quiz

    Good evening. I'd like to first start by saying I am new to this forum, and I am a physics noob. I know that very fact will help people shy away from trying to help me answer this question. This problem (which an image is posted) is 1 of 5 questions on a take home kinematic quiz. I've managed to...
  44. E

    Example of x0 in the kinematic equation for displacement

    In the kinematic equation x = x0 + v0 * t + .5 * a * t^2, can someone give me an example in which x0 has a value that is not zero?
  45. H

    Kinematic questions(velocity of 2 contact points)

    in the picture below http://tinypic.com/view.php?pic=9riq9l&s=6 if we know the angular velocity of the gear on the left, as well as their current distance from contact point, what can we say about the velocity of the right rod at the contact point at anytime t? we know it is not...
  46. H

    Calculating Car Acceleration: Kinematic Equations

    Homework Statement You are driving your car and you heavily apply the brakes for a period of 2.1 seconds. The car keeps moving for a distance of 14.6m before it completely stops. What is the acceleration (in m/s2) experienced by the car? Is it truly "acceleration"?Homework Equations 5...
  47. R

    How Do I Solve This Kinematic Equation Problem with Gravity?

    So I'm given... In the y-direction vo = 0 m/s vf = 7.5 m/s (is the speed of the ball thrown straight up) g = -9.81 m/s2 (when it falls back down) yo = 0 m yf = 1.5 m (at this height above the ground, the bat connects with the ball) t = ? I tried doing this... yf = yo + vyot +...
  48. J

    Kinematic Equation vs. Delta velocity / Delta Time - Factor of 2?

    I am testing a cylindrical piece of steel dropping down steel pipe in a vacuum system, and came across a problem comparing the kinematic equation and a standard change in velocity over change in time to determine an acceleration. My derivation shows that the kinematic equation is exactly 2...
  49. S

    Ten Kinematic Problems Grade 12 Physics

    Homework Statement See attachment, it is the question sheet. Homework Equations vf^2=vi^2+2ad d=vit+1/2at^2 vf=vi+at d=vit-1/2at^2 d=vavt The Attempt at a Solution 1. An object such as a ball let go by a person's hand falling vertically downward toward Earth has a velocity and...
  50. M

    Help with calculating vertical jump with kinematic equations

    Ok, so I'm using an arduino with an led matrix and a homemade pressure sensor to figure out the height of a vertical jump and then display the info back. First I get the amount of time between when the person left the board and when they land back on it. I then divide the time in half and use...
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