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.

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  1. tomo

    2 questions regarding circular motion and Newton's 1st Law

    Hey, I'm an adult who finally realized that physics is great and tries to recall (or rather learn for the first time) what he learned at the school. I've been reading some basic things around. It's not really a homework question, I'm just trying to understand the laws here. 1. I know that if a...
  2. N

    Velocity is proportional to distance

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  3. Ritzycat

    When Do Rocket Cars with Different Accelerations Meet?

    Homework Statement A "rocket car" is launched along a long straight track att = 0 s. It moves with constant acceleration a1 = 2.9m/s2 .At t = 2.8s , a second car is launched with constant acceleration a2 = 7.0m/s2 . At what time does the second car catch up with the first one? How far down the...
  4. M

    Kinematics Equations and a Cliff

    Homework Statement A car drives off a cliff that is 100m high. It has to land in water and the water starts 30m away from the cliff. Its goal is to land 90m into the water. How fast must the car be going to land at that point in the water. Air resistance is negligible. v=0 v0=? a= -9.91m/s2...
  5. abram

    Fundamental kinematics question

    Homework Statement I seem to have a fundamental misunderstanding of the kinematic principles in this question. A constant force of 8.0N is exerted for 4.0s on a 16-kg object initially at rest. What will the change in speed of this object be? Homework Equations F = ma Δx = v0t + 1/2 at2 Δv =...
  6. S

    Rotational kinematics (mass wrapped around inner hub)

    Homework Statement A bicycle wheel is mounted as in the lab and as shown to the right. This wheel has a mass of 6.55 kg, a radius of R = 38.0 cm and is in the shape of a ring. A mass M = 1.85 kg is attached to the end of a string which is wrapped around an inner hub which has a radius r = 5.40...
  7. R

    Kinematics Book Question -- Rowing a boat across a river at an angle

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  8. Matt atkinson

    Beta+ meson, decay - Relativistic kinematics

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  9. Y

    Kinematics using vector analysis

    Homework Statement Homework Equations Va = Vb + Va/b Va = Vb + (wab x ra/b) The Attempt at a Solution OK so here is part of my solution: My velocity for B is correct according to the book. But I'm confused about D. The only problem here is that the velocity of D only has an i...
  10. Q

    I have a big question(Dynamics-Parallel Velocities)

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  11. gracy

    Accel Due to Gravity When Obj Touches Ground

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  12. R

    How can you accurately find the initial velocity of a toy gun?

    Disregarding air resistance, how could you find an accurate number for the initial velocity of a toy gun?
  13. Z

    Motion level forward kinematics on Simulink

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  14. D

    Force and Motion problem

    1. A 1 kg wedge is pulled across a rough floor (uk=0.20) via contact with a 2 kg block as shown below. The shape of the wedge is that of an isosceles right triangle. a rope passes from the 2 kg block and over a mass-less and friction-less pulley and is attached to a hanging mass. Find the...
  15. N

    How Can You Calculate the Length of a Ramp Based on Sliding Time and Friction?

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  16. AdityaDev

    Air Drag & No Drag on a Ball Projected Vertically

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  17. A

    Simple projectile motion question

    Homework Statement A missle is fired vertically up from a ground with an initial velocity of 20m/s. The acceleration at any time is given by dv/dt = -10 + t/2 m/s^2. Find the height of the missile after two seconds Find the height after four seconds the direction the missile is traveling when t...
  18. B

    Crash Test Craig drives his 800kg car up a 100m ramp. Help?

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  19. CitrusLime

    Calculating Angular Velocity & Acceleration of Rotating Frame-B

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  20. G

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  21. Z

    Kinematics of pantograph device

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  22. E

    Kinematics, solving for theta

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  23. D

    Finding the distance between two points in terms of variables

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  24. D

    Kinematics Question. Incline, Spring, Friction

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  25. J

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  26. M

    Measuring Torque from a Servo

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  27. N

    Circular motion of a steel block

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  28. S

    Maximize Stone's Height Thrown From 56m Building - 2d Kinematics Help

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  29. Hijaz Aslam

    Is relative velocity confusing in multiple vector systems?

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  30. 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...
  31. D

    Work and Kinematics: Do Both Stones Hit the Ground at the Same Time and Speed?

    Homework Statement A stone is thrown straight up from the roof of a building with initial speed v0. At the same instant, a second stone is thrown from the roof upward at an angle of 60o with the horizontal and with the same initial speed v0. Which is correct? both stones hit the ground at the...
  32. J

    Finding the Optimal Archer Angle for Hitting a Moving Target on Planet Zorg

    Hello everybody. Although this is just a kinematics problem, I am having a hard time figuring out what to do. The question is: An archer on the planet zorg spots an octomorph that is resting in a tree above water. The octomorph's position in the tree is 100m away horizontally and 100m...
  33. B

    Vectors and finding relative speed

    Homework Statement Find Particle A's speed with respect to Particle B. I am given: Particle A: (15i - 10j) or 18.03 m/s angle A: -33.69 degrees Particle B: (5i + 15j) or 15.81 m/s angle B: 71.57 degrees (Both angles with respect to x axis) Homework Equations Had there not been any angles, I...
  34. B

    Solving for Particle A's Speed with Respect to Particle B

    Very simple question but I am confused... I am asked to find Particle A's speed with respect to Particle B. What does this mean? I am given: Particle A: (15i - 10j) or 18.03 m/s Particle B: (5i + 15j) or 15.81 m/s I just don't understand what I'm being asked to find and how to go about solving...
  35. M

    How Tall Is the Building If a Brick Is Thrown Upward?

    Homework Statement A brick is thrown upward from the top of a building at an angle of 23.8 degrees above the horizontal and with an initial speed of a 14.2 m/s. Acceleration of gravity is 9.8 m/s/s. If the brick is in flight for 3.3 s how tall is the building? Homework Equations...
  36. F

    What is the initial velocity of the ball on a smooth ramp?

    Hi, I am new to Physics. I'm having trouble solving these word problems. For the third question I need to find the time first and then the initial velocity? 1. A young girl gives her toboggan a push of 4.0 m/s up a hill. It slides up the hill slowing down at an acceleration of 8.0 m/s2...
  37. T

    2 dimensional kinematics involving a rocket

    Homework Statement A rocket is initially at rest on the ground. At time = 0, its engines ignite causing the rocket to move in a straight line with constant total acceleration of a = 30 m/s^2 at an angle of 76 degrees, and the engines are strong enough to counter gravity and keep it exactly in a...
  38. A

    Solving for ds/dt: Is the Answer C?

    Homework Statement http://puu.sh/c0mFR/515cf5fd15.png Homework Equations ds/dt=dv The Attempt at a Solution I think answer is C by observation. Is it correct? if not what is the answer[/B]
  39. R

    Kinematics Problem -- 3 particles at the vertices of an equilateral triangle

    Here's the question: Three particles A, B and C are situated at the vertices of an equilateral triangle ABC of side d at time t = 0. Each of the particles moves with constant speed v. The particle at A always has its velocity along AB, B along BC and C along CA. At what time will the particles...
  40. Satvik Pandey

    A kinematics problem in which direction of velocity keeps changing.

    Homework Statement A dog sees a rabbit running in a straight line across an open field and gives chase. In a rectangular coordinate system (L,0), assume: (i) The rabbit is at the origin and the dog is at the point at the instant the dog first sees the rabbit. (ii) The rabbit runs up the...
  41. A

    Kinematics Acceleration question

    Homework Statement Suppose a can, after an initial kick, moves up along a smooth hill of ice. Make a statement concerning its acceleration. A) It will travel at constant velocity with zero acceleration. B) It will have a constant acceleration up the hill, but a different constant acceleration...
  42. A

    Two Balls Drop, what happens to the distance?

    Homework Statement Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the distance between them A) increases. [<-- Correct Answer] B) remains constant. C) decreases. D) cannot be determined from the information given...
  43. K

    ID Kinematics: Chasing a Mouse

    Homework Statement An old fox resting near a road sees a mouse that is traveling at a speed of 1.3 km/h. At the moment the fox sees the mouse , it starts chasing after it . The fox's acceleration is 0.45 m/s^2. a) how much time is elapsed between when the fox start's to when the mouse is...
  44. T

    1d Kinematics Homework: Helicopter mailbag

    Homework Statement The height of a helicopter above the ground is given by h = 3.30t3, where h is in meters and t is in seconds. After 1.80 s, the helicopter releases a small mailbag. Assume the upward direction is positive and the downward direction is negative. Already solved for Initial...
  45. B

    Physics car problem kinematics

    1. The problem statement, all You drive on Interstate 10 from San Antonio to Houston, half the time at 65 km/h and the other half at 117 km/h. On the way back you travel half thedistance at 65 km/h and the other half at 117 km/h. What is your average speed (a) from San Antonio to Houston, (b)...
  46. SSundee

    Kinematics: Initial Velocity, Acceleration, Displacement & Time

    Hello All, A lot of you are probably physics majors so this question will sound dumb to you, but I am just in A.P. Physics 1 in high school... we are learning projectile motion and the teacher is not the best at explaining it. We had our first test a few days ago, everyone bombed it, and he...
  47. Ritzycat

    How Do You Calculate the Minimum Speed of a Baseball for a Home Run in Physics?

    I'm struggling to do this problem. "When Babe Ruth hit a homer over the 7.0m -high right-field fence 120m from home plate, roughly what was the minimum speed of the ball when it left the bat? Assume the ball was hit 1.0m above the ground and its path initially made a 30∘ angle with the ground."...
  48. R

    Physics HW kinematics and sig figs

    Homework Statement An indestructible bullet 2.10cm long is fired straight through a board that is 11.7cm thick. The bullet strikes the board with a speed of 416m/s and emerges with a speed of 296m/s.Homework Equations What is the total time that the bullet is in contact with the board? What...
  49. C

    Solving for the Velocity and Height in a Difficult Kinematics Problem

    Homework Statement In the figure, a ball is thrown leftward from the left edge of the roof, at height h above the ground. The ball hits the ground 1.07 s. later, at distance d = 27.5 m from the building and at angle θ = 67° with the horizontal. (a) Find h (b) What is the velocity at...
  50. D

    Dynamics class w/o kinematics equations?

    Homework Statement My problem is I don't understand what my professor wants us to do instead. He says that we don't need to memorize any equations, namely the equations of motion, and that everything can be solved with basic principles and integration. The problem is, I have no idea how to...
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