What is Kinematics: Definition and 1000 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.

View More On Wikipedia.org
Recent contents Top users
  1. K

    Kinematics - projectile motion - time to maximum height?

    Kinematics -- projectile motion -- time to maximum height? Homework Statement The nozzle of a fire hose discharges water at a speed of 10 m/s. The nozzle is aimed straight up. How long does it take for a water drop to reach its maximum height? Start with translating the question: vi= 10 m/s...
  2. K

    Kinematics - How fast does the car stop?

    Kinematics -- How fast does the car stop? Homework Statement A car is moving with a speed of 32.0 m/s. The driver sees an accident ahead and slams on the brakes, giving the car an acceleration of -3.50 m/s2. How far does the car travel after the driver put on the brakes before it comes to a...
  3. R

    2D Kinematics Problem involving subtended angle

    Homework Statement Mortar crew is near the top of a steep hill. They have a mortar. They angle this mortar at an angle of \theta = 65° . The crew fires a shell at a muzzle velocity of 228 ft/sec (69.5 m/s). How far down the hill does the shell strike if the hill subtends an angle of \phi =...
  4. K

    2D Kinematics - 2 rocks off a bridge

    2D Kinematics -- 2 rocks off a bridge Homework Statement Heather and Jerry are standing on a bridge 60m above a river. Heather throws a rock straight down with a speed of 14m/s . Jerry, at exactly the same instant of time, throws a rock straight up with the same speed. Ignore air...
  5. L

    MHB How Do You Calculate When and Where a Car Catches Up to a Truck?

    A car is stopped at a traffic light in the moment in which a truck which has a constant speed of 50 Km/h passes throught a trafic light light eats and passes the car 10.s later the traffic light changes and the car accelerates to 2 m/s2 for 15 sec then which, it continuous your travel at...
  6. K

    Kinematics - centrifuging a solution with bacteria

    Kinematics -- centrifuging a solution with bacteria Homework Statement In the lab, we have to separate the bacteria from the solution by centrifuging the solution with bacteria. Because the bacteria are more massive than the media molecules, they settle to the bottom of the container. For...
  7. S

    Calculating Collision Time for Two Objects with Different Initial Velocities

    Homework Statement Two balls are thrown upwards from the same spot 1.15 seconds apart. The first ball had an initial velocity of 15.0 m/s and the second was 12.0 m/s. At what time do they collide? 2. The attempt at a solution a = first ball b= second ball For them to collide, their height...
  8. C

    Problem on kinematics of body falling from space

    Problem goes like this.. body falls toward a planet with acceleration of -g0*R^2/s^2. where R is the radius of planet 4000 miles, g0 is 30 ft/s^2, s is the distance of the body from the planets center. the initial distance of the body from the surface is 400 miles. find the impact velocity...
  9. S

    Applying Kinematic Equations: Calculus-Based Physics Homework Problems

    Homework Statement I currently have a few problems I am working on for my calculus based physics class. I'm duel enrolling in both calc based physics and calc at this moment. |||The first problem is The figure (figure 1) shows the motion diagram, made at two frames of film per second, of a...
  10. M

    Kinematics Problem: Finding Initial Velocity of a Basketball Thrown at an Angle

    Hey, so I've been having some problems with Kinematics in reviewing for my finals next week! One question in particular I need help with, because I don't know how to solve it, and I am very bad at conveying my solutions on tests. Can anyone give me a hand? The question is : a basketball...
  11. KiNGGeexD

    Angular Kinematics: Calculating Car's Angular Acceleration

    Question The wheel of a car has radius 0.2m and initially rotates at 120 rpm. In the next minute it makes 90 revolutions What is the cars angular acceleration?Attempt So I tried to get the final angular velocity and couldn't and have tried multiple times with the angular kinematics equations...
  12. P

    What is the significance of h in relation to finding the distance AB?

    Homework Statement http://postimg.org/image/bh4tzmd4l/ Can someone explain to me what "acceleration of the truck relative to the crate means"? What should I do first in trying to solve this?
  13. T

    Why Does Zero Integration of a Velocity-Time Graph Not Confirm Return to Origin?

    Say you have a v-t diagram for the motion of a particle in one dimension where the velocity is positive at first and then negative later. If you integrate and get zero, why doesn't that mean that the particle started moving and then came back to the origin?
  14. T

    How to Determine if a Particle Has Returned to the Origin?

    Homework Statement A point begins at rest at x = 0 and accelerates at 1.09 m/s^2 to the right for 10 s. It then continues at constant velocity of 10.9 m/s for 8 more seconds. In the third phase of its motion, it decelerates at 5 m/s^2 and is observed to be passing again through the origin when...
  15. T

    Kinematics Problem: Sprinter Acceleration and Velocity

    Ok so I have this problem which is most likely easy to all of you. The problem says that the first 10 meters of the 100 meter are covered in the first 2 seconds by a sprinter who starts from rest and accelerates with a constant acceleration. The remaining 90 meters are run with the same velocity...
  16. C

    Solve Kinematics Problem: Subway Train, Unbanked Curve, 15° Angle

    A subway train rounds an unbanked curve at 67km/h. A passenger, hanging onto a strap notices an adjacent strap is unused and makes an angle of 15° to the vertical. What is the radius of the turn? Relation of sines, opposite and hypotenuse of a right triangle. Opposite...
  17. G

    Kinematics of Relativity: Deriving Dilation Time

    I'm about to ask derivation of dilation time in terms of Special Relativity. I saw explanations in Introduction to Classical Mechanics by David Morin that dilation time is formed by assumption that light speed is absolute refers to all inertial reference. He derived it by comparing 2...
  18. jaumzaum

    Kinematics of a dipole - Wopho Problem

    This problem is originally from Wopho and its goal is to describe the trajectory of a point mass charge around a dipole. http://img18.imageshack.us/img18/2676/fvac.png First we have to calculate the radial and tangential electric fields made by the dipole (this I've done as well) but...
  19. I

    Kinematics - Projectile Motion

    Question: A cannon, located ##60.0 m## from the base of a vertical ##25.0 m## tall cliff, shoots a ##15 kg## shell at ##43.0°## above the horizontal toward the cliff. What must the minimum muzzle velocity be for the shell to clear the top of the cliff? I have attempted a solution that I'm...
  20. S

    Kinematics - Velocity, force of gravity, terminal speed

    Hi everyone, I would really appreciate any advice on how to go about solving the following problem. I'm supposed to investigate it in a report. Homework Statement A paratrooper who jumps out of an aircraft moving in horizontal flight initially has the same horizontal velocity as the aircraft...
  21. W

    Kinematics (rectilnear motion) spring.

    the 14 in. spring is compressed to an 8 in length, where it is released from rest and accelerates black A. the acceleration has an initial value of 400ft/sec^2 and then decreases linearly with the x-movement of the black, reaching zero when the spring regains its original 14 in. length...
  22. W

    Kinematics (rectilnear motion) simple

    Ball 1 is launched with an initial vertical velocity v1=160 ft/sec. Three seconds later, ball 2 is launched with an initial velocity v2. determine v2 if the balls are to collide at an altitude of 300ft. not sure where I am going wrong, do I have my limits...
  23. K

    Understanding Kinematics Graph Analysis

    Homework Statement Here is the question.. Figure P2.35 (A link to the image is posted) represents part of the performance data of a car owned by a proud physics student. (a) Calculate the total distance traveled by computing the area under the red-brown graph line. (b) What distance does the...
  24. N

    Kinematics motion-an object falling and crossing a camera's view

    Homework Statement You're a consultant on a movie set and the producer wants a car to drop so that it crosses the camera's field of view in time Δt. The field of view has height h. Derive an expression for the height above the top of the field of view from which the car should be released...
  25. N

    Kinematics motion-setting up instantaneous velocity function

    Homework Statement An object starts moving in a straight line from position xi, at time t =0, with velocity vi. Its acceleration is given by a = ai + bt, where ai and b are constant. Find expressions for a)instantaneous velocity b) position as functions of time. Homework Equations...
  26. N

    Kinematics motion-police's radars(answer check)

    Homework Statement A police radar's effective range is 1km and your radar detector's range is 1.9km. You're going at 110kmh^-1 in a 70kmh^-1 zone when the detector beeps. At what rate must negatively accelerate to avoid a speeding ticket? Homework Equations none The Attempt at a...
  27. N

    Kinematics motion-falling balloon (answer check)

    Homework Statement A balloon takes 0.22s to cross a 1.3m high window. From what height above was it dropped? Homework Equations None. The Attempt at a Solution
  28. N

    Kinematics motion - Dancers pausing at top of their leap

    Kinematics motion -- Dancers pausing at top of their leap Homework Statement Ice skaters, ballet dancers, and basket ball players executing vertical leaps often give the illusion of "hanging" almost motionless near the top of the leap. To see why this is, consider a leap to maximum height, h...
  29. M

    Dynamics Module - Kinematics Problem

    Hi, I have an basic kinematics problem I can't seem to grasp -- hopefully someone can shed some light on it for me? The acceleration, a, of an object is equal to a=s, where s is the distance from the start position. Sketch a graph representing velocity against distance, s, for the...
  30. I

    Why Kinematics is So Popular in the Homework Forum

    Everytime I go into the homework questions forum and look at threads started by people it always makes me laugh what threads have so many comments. In the introductory physics forum when it's a question on kinematics, there's always like 10 people that answer. As soon as there's something about...
  31. N

    Kinematics motion - Given position, find velocity and acceleration

    Kinematics motion -- Given position, find velocity and acceleration Homework Statement A particle's position as a function of time is given by xf = xi . sin wt, where xi and w are constants. a) Find expressions for velocity and acceleration. b) What are the maximum values of velocity...
  32. N

    Kinematics Motion Average Speeds

    Homework Statement Consider an object traversing a distance L, part of the way at speed v1 and the rest of the way at speed v2. Find expressions for the average speeds when the object moves at eac of the two speeds. a) for half the total time b) for half the distance Homework...
  33. N

    How Fast Must a Book Be Tossed to Clear a Windowsill?

    Homework Statement A book is toss into your dorm room, just clearing a windowsill 4.2m above ground. a)If the book leaves your hand 1.5m above ground, how fast must it be going to clear the sill? b)How long after it leaves your hand will it hit the floor, 0.87m below the windowsill...
  34. Ascendant78

    Solving for an angle in 2-D kinematics

    Homework Statement At the buzzer, a basketball player shoots a desperation shot. She is 14m from the basket and the ball leaves her hands exactly 1.4m below the rim. She throws the ball at 18m/s. Can she make the shot? (Solve for necessary angle) Homework Equations r2y = r1y + v1y(t2)...
  35. N

    How Fast Were the Trains Moving at the Point of Collision?

    Homework Statement You're an investigator for the National Transportation safety board, examining a subway accident in which a train going at 80kmh^-1 collided with a slower train traveling in the same direction at 25kmh^-1. Your job is to determine the relative speed of the collision to help...
  36. D

    Can Rotation Affect the Linear Motion of an Object's Center of Mass?

    Homework Statement This isn't so much of a problem as a general question. I am trying to find the starting velocity of a spinning ball going upwards (in air, close to Earth's surface, only force acting on it is the gravitational force) until its linear velocity reaches zero. I found the initial...
  37. N

    Rocket Launch Kinematics motion

    Homework Statement You're at a mission control for a rocket launch, deiciding whether to let the launch proceed. A band of clouds 5.3km thick extends upwards from 1.9km altitude. The rocket will accelerate at 4.6ms^-2 and it isn't allowed to be out of sight for more than 30s. Should the...
  38. N

    Kinematics: Catch Ball Dropped from Balloon After 24.7s

    Homework Statement A balloon is rising at 10m/s when its passenger throws a ball straight up at 12m/s relative to the balloon . How much later does the passenger catches the ball? Homework Equations The Attempt at a Solution vf^2 - vi^2 = 2g(yf-yi) Ball: 0ms^-1 - (22ms^-1)^2 =...
  39. N

    How Do Two Divers' Speeds Compare When Jumping from a 3m Platform?

    Homework Statement Two divers jumped from a 3m platform. One jumps upward at 1.8ms^-1 and the second steps off the platform as the first passes it on the way down. a) What are their speeds as they hit the water? b) Which hits the water first and by how much? Homework Equations...
  40. N

    Dropped ball Kinematics motion

    Homework Statement You're atop a building of height, h, and a friend is poised to drop a ball from a window at h/2. Find an expression for the speed at which you should simultaneously throw a ball downward, so the two hit the ground at the same time. Homework Equations None The Attempt at a...
  41. N

    Falling object Kinematics motion

    Homework Statement A falling object travels one-fourth of its distance during the last second of its fall. From what height was it dropped? Homework Equations none The Attempt at a Solution yf - yi = vit + 0.5gt^2 0.25x = 0 + 0.5(-9.8ms^-2)(1)^2 x = 19.6m
  42. N

    Car Distance Kinematics motion

    Homework Statement You're speeding at 85km/h when you notice that you're only 10m behind the car in front of you which is moving at the legal speed limit of 60km/h. You slam on your brakes and your car negatively accelerates at 4.2m/s/s. Assuming the other car continues at constant speed, will...
  43. Z

    Rotational Kinematics of a turntable

    Good afternoon! I've been mulling over this question for a bit and I can't seem to understand what it is asking. This is a question for an introductory calculus-based physics university course. 1. The Problem: A uniform disk, such as a record turntable, turns 8.0 rev/s around a frictionless...
  44. N

    Speed Up to Catch Leader in 10km Race

    After 35mins of runnin, at the 9km point in a 10km race, you find yourself 100m behind the leader and moving at the same speed. What should your acceleration be if you're to catch up by the finish line? Assume that the leader maintains constant speed.
  45. N

    Kinematics Motion: Stopping a Puck Moving at 32m/s

    Homework Statement A puck moving at 32m/s slams into a wall of snow 34cm thick. it emerges moving at 18m/s. Assuming constant acceleration, find a) time taken for puck to spend in the snow (ans:0.014s got it) b)the thickness of a snow wall that would stop the puck entirely Homework...
  46. N

    Reducing Stopping Time with Antilock Brakes

    Hi, I'm an undergraduate commencing my first year in Astrophysics and Mathematics. It's the summer break as of now and I'm doing some self-study on the relevant topics when school commences. Homework Statement On packed snow, computerized antilock brakes can reduce a car's stopping...
  47. F

    Simple kinematics with friction

    Homework Statement A stack of two blocks sits on a frictionless surface; however, between the two blocks is a kinetic coefficient of friction μk. External force F is applied to the top block. During the time the force is applied, the top block is displaced by x1, and the bottom block is...
  48. N

    Rotational Kinematics - Angular Acceleration

    Homework Statement A phonograph turntable with an initial angular velocity of 78 rpm continues turning for 40 rotations after being switched off. What is the angular deceleration of the turntable? Assume constant angular deceleration. Homework Equations \alpha=(\omega-\omega0)/t...
  49. O

    Kinematics of mass on a semi-circular slide

    Homework Statement A mass slides down a segment of a circle starting from rest at A. It has a radius of R. Find the speed of the mass at the bottom ignoring friction. Also, find the time for the ice cube to go from A to B. As far as solving for the time I am told not to calculate the...
  50. J

    Calling all physics teachers: interesting kinematics lessons?

    I am not sure where else to post this. Hopefully this is not in the wrong place. I am student teaching in a physics classroom this week. I will be teaching about scalars vs. vectors, calculating average velocity, and calculating acceleration. As I plan my lessons, I've realized they are...
Back
Top