What is Kinematic: Definition and 405 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. D

    Kinematic problems with angles

    This is my first year taking a Physics class, so this might just be a simple question but I'm stuck. Homework Statement A stunt driver wants to make his car jump over eight cars parked side by side below a horizontal ramp. (a) With what minimum speed must he drive off the horizontal...
  2. P

    Solve Kinematic Equations for Automobile Braking

    Homework Statement An automobile is traveling on a long, straight highway at a steady 75.0 mi/h (33.3 m/s) when the driver sees a wreck 150m ahead. At that instant, she applies the brakes (ignore reaction time). Between her and the wreck are two different surfaces. First there is 100m of...
  3. P

    Kinematic Equations (Constant Acceleration)

    Homework Statement The speed limit in a school zone is 40 km/h (about 25 mi/h). A driver traveling at this speed sees a child run onto the road 13m ahead of his car. He applies the brakes, and the car decelerates at a uniform rate of 8.0 m/s^2. If the driver's reaction time is 0.25 seconds...
  4. F

    Basic physics logic help - kinematic equations and forces

    Homework Statement A small object, of mass 0.02Kg is at the top of a tall structure 160m high, it is dropped from rest. Ignoring air resistance.. 1. Find the speed of the object as it hits the ground 2. find the time taken Homework Equations So far we have learned the equations...
  5. D

    Why Do Different Kinematic Equations Yield Different Results for Free Fall?

    Homework Statement Upton Chuck is riding the Giant Drop at Great America. If Upton free falls for 2.6 seconds, what will be his final velocity and how far will he fall? Homework Equations The Attempt at a Solution Finding V(final)= Vf-Vi = at ---> Vf = (-9.81)(2.6) = 25.5 The...
  6. M

    Kinematic and Projectile motion equations

    Homework Statement Find the angle of the projection for which the maximum height is equal half of the range. Homework Equations Kinematic and Projectile motion equations
  7. D

    Confusing regarding Kinematic Equations

    "A 93kg water skier floating in a lake is pulled from rest to a speed of 13 m/s in a distance of 20m. What is the net force exerted on the skier, assuming his velocity is constant. So I know I have to find the force I'm going to need acceleration, and to find it I'll need to use a kinematic...
  8. M

    What is the maximum height of the stadium at its back wall?

    Homework Statement Ted Williams hits a baseball with an initial velocity of 120 miles per hour (176 ft/s) at an angle of θ = 35 degrees to the horizontal. The ball is struck 3 feet above home plate. You watch as the ball goes over the outfield wall 420 feet away and lands in the bleachers...
  9. M

    Complex Kinematic problem for grade 12 phyiscs

    a daredevil motorcyclist attempts to leap a 48m wide gorge. At the side where the cyclist starts, the ground slopes upward at an angle of 15 degree. beyond the far rim, the ground is level and is 5.9m below the near rim. what is the minimum speed necessary for the cyclist to clear the gorge[b]
  10. M

    Finding the kinematic degree of indeterminacy?

    I am currently looking at this website: http://www.public.iastate.edu/~fanous/ce332/displ/homepage.html And this example that they went through: http://www.public.iastate.edu/~fanous/ce332/displ/homepage.html Why does that structure only have one degree of kinematic indeterminacy? I...
  11. M

    One-D Kinematic Question w/ rising hot air balloon

    Homework Statement A hot-air balloon has just lifted off and is rising at a constant rate of 2.3m/s. Suddenly, one of the passengers realizes she has left her camera on the ground. A friend picks it up and tosses it straight upward with an initial speed of 14m/s. If the passenger is 2.5m...
  12. B

    Average G-Force Calculation for Abrupt Deceleration from 30mph in 1m Distance

    Homework Statement Determine the average number of g's experienced by someone abruptly coming to rest from an initial velocity of 30mph (such as in a car crash). Take the distance involved in coming to rest to be 1 m. Homework Equations V=Vo+at ΔS=VoT+1/2at^2 V^2=Vo^2+2aΔS The Attempt...
  13. C

    Kinematic Momentum: Is Mass x Volume Correct?

    Hey I just wanted to check with y'all, but I feel I'm fairly well acquainted with momentum and the rules surrounding it, but in brushing up I began reading the wiki article on it. In the generalized momentum section I came across the term kinematic momentum described as mass times volume...
  14. W

    At What temperature will air get a larger kinematic viscosity than crude oil?

    Homework Statement At What temperature will air get a larger kinematic viscosity than crude oil? Please explain step by step. I believe we have compare the viscosity of air and the oil using the formula: kinematic viscosity = dynamic viscosity / density Homework Equations inematic...
  15. A

    Complex number method for kinematic equations

    Homework Statement Objective: 1. For a two-arm manipulator, use complex-number method to derive the displacement, velocity and acceleration equations for the tracing point P. 2. For a two-arm manipulator, use complex-number method to derive the displacement, velocity and acceleration equations...
  16. W

    Significance of kinematic and dynamic viscosity

    It is stated that kinematic viscosity is the ratio of dynamic viscosity to density. can anyone elaborate it further that what are the uses of both types of viscosities and why we differentiate them.does dynamic viscosity reates with static fluid?
  17. B

    .Solving for Initial Velocity: Kinematic Equations

    how to get to Vo = the square root of ((xa)/(sin2theta)) from the kinematic equations or form SinTheta =Voy/Vo CosTheta =Vox/Vo just really confused. I am writing a formal lab for my final and what I am asking is find the initial velocity it would take for the object to hit the target as a...
  18. K

    How can i use kinematic equations to solve this problem?

    Hello everyone, This is my first post so I am sorry if this is in the wrong section. I am currently in a rush to finish my homework. I have tried working on it for several hours but I still cannot figure it out. I am mainly trying to figure out how long the object will be in the air. A...
  19. 7

    How Far Must a Skier Travel to Reach 56 m/s on a 30° Slope?

    Homework Statement A skier reaches a speed of 56 m/s on a 30° slope w/ no friction. What is the minimum distance the skier would have to travel if starting from rest. Homework Equations Vf2 = Vi2 +2(a)(Δd)The Attempt at a Solution I hope no one will scoff too hard, this is my first physics...
  20. H

    Solve Kinematic Problems: Tips & Advice

    Hello, I'am doing some selfstudy to aqcuire more experience with mechanics. I got a geat book I'am currently reading. But got stuck in a question I can't answer... I hope you guys can get me on the good track, just need an approach to tackle te problem. Did already solve problems,but...
  21. C

    What is the kinematic conditions for free-surface

    When I am studying the Rayleigh-Taylor instability, I saw this equation: \frac{\partial \eta}{\partial t} + u' \frac{\partial \eta}{\partial x} = \omega ' (\eta) I do not quite understand the meaning of this equation. Can some one provide me with some instructions and information...
  22. M

    How do I solve basic kinematic problems with projectile motion?

    I understand many of you may take me for a fool since this is a practically elementary physics problem but I really need some help finding out the right formulas or formula to solve it. No answers though, I actually want to learn this stuff. Problem: You shoot an arrow into the air. After...
  23. A

    Calculating velocity, time, and Instantaneous speed using kinematic equations

    Homework Statement An inquisitive physics student and mountain climber climbs a 52.0-m-high cliff that overhangs a calm pool of water. He throws two stones vertically downward, 1.00 s apart, and observes that they cause a single splash. The first stone has an initial speed of 2.10 m/s...
  24. V

    Please explain this Kinematic Problem.

    How far do you travel if, starting from rest, you accelerate at 1.5 m/s2 for 4.0 s, then coast for 8.0 seconds, then decelerate to a standstill in 4.0 s? I am totally confused about the fact you accelerate and then coast, and then slow down. We have 3-t's in this problem and don't know what...
  25. A

    How can I easily derive the kinematic equations for constant acceleration?

    I'm tired of having to look up the kinematic equations every time I need to use them (I tutor lower devision students a lot). Is there an intuitive and memorable way to derive them? As in, it's easy to derive x=x0+v0t+at2 just by integrating a constant force. Can I get the others without...
  26. S

    Kinematic One-D Problem: Calculating Total Distance Run by Dog in Morning Run

    Homework Statement A women and her dog are out for a morning run to the river, which is located 4km away. The women runs at 2.5m/s in a straight line. The dog is unleashed and runs back and forth at 4.5m/s between his owner and the river, until the women reaches the river. What is the total...
  27. L

    Calculating Range of Santa's Roof Slide: An Energy Conservation Approach

    Homework Statement Santa has an unfortunate roof mishap. When he steps out of his sleigh, he realizes that there is a coating of ice on this particular roof—making it a completely frictionless surface. Starting with an initial velocity of zero, he slides down the roof (a distance of 2.50 m...
  28. V

    Kinematic Equation Homework Question

    Homework Statement Gwen releases a rock at rest from the top of a 40 m tower. If g = 9.8 m/s2 and air resistance is negligible, what is the speed of the rock as it hits the ground? v0 = initial velocity = 0 a = acceleration = 9.8 Δy = displacement in y direction = -40 v = final velocity =...
  29. D

    Planar Kinematic Modelling Question

    Homework Statement Please see the picture shown below: Homework Equations I know the inertias of the AO and BO beams w/ respect to O are both 1/3*ml^2, but what are the inertias of AC and BC w/ respect to O?The Attempt at a Solution Any other hints that you guys have for solving a problem like...
  30. M

    Question about kinematic equation

    Assuming initial angular velocity is 0 I want to solve for final position theta Ang Acceleration = Δw/Δt = w/t w = Δ(theta)/Δt = theta/t ang acc = theta/t^2 theta = (ang acc)(t^2) but how come the kinematic equation is...theta = (ang acc)t^2/2 Where did my 2 go?
  31. H

    Kinematic Problem: Finding Average and Instantaneous Velocity

    Homework Statement An airplane maintains a constant acceleration of 4.0m/s^2 as it speeds up from 16m/s [E] to 28 m/s [E]. A what is the average velocity? b) how long does the airplane accelerate? c) when is the instantaneous velocity equal to the average velocity for the interval? a= 4.0...
  32. M

    Kinematic Equations Rearrangment

    Homework Statement A= Acceleration Vf = Final Velocity Vi = Initial Velocity D= Displacement T = Time Homework Equations D=Vf*T - 1/2*a*(t)2 Solve for T The Attempt at a Solution I need to solve for T: This is what I got as my attempt but it is so very wrong still...
  33. R

    How Long Does It Take for Two Cars to Meet in a Kinematic Problem?

    Homework Statement Car a: starts moving from rest, acceleration= 4.5m/s², starting distance = 0m car b : constant velocity of 25m/s, starting distance = 75m How long will it take car b to catch up with car a?
  34. N

    How Do Friction and Tension Affect Motion in Physics Problems?

    Homework Statement q1: A hockey player shoots a 200 gram puck at 25m/s. the ice has a friction of 0.09 kinetic. how far will the puck slide before it comes to a rest? q2: A train has 3 cars, mc, mb, and ma. The acceleration of the train is 1.54 m/s^2. ma has a mass for 10kg, mb a mass of...
  35. U

    How Do You Calculate Displacement, Average Speed, and Velocity in 2D Kinematics?

    A motorist drives south at 20.0m/s for 3.00 min, then turns west and travels at 25.0m/s for 2.00 min, and finally travels northwest at 3.00m/s for 1.00 min. For the 60 min trip, find the total displacement, the average speed and the average velocity. I'm embarrassed how I still don't...
  36. I

    Do two hockey pucks on a frictionless plane collide and when?

    This is not for an assignment as much as my own edification, but as it is a homework-style question, I thought this would be the best place. If not, I apologize. Homework Statement Given two hockey pucks of radius R1 and R2 on a frictionless, infinite level plane, located at (X1,Y1) and...
  37. G

    Tips on solving 2D Kinematic problems

    Hi, This isn't a homework question. I need help on how to go about solving 2D kinematics problems. My teacher is terrible and doesn't even teach. It seems like it should be pretty straight forward with solving these, but I'm just having a hard time. If someone could give me tips on how to...
  38. E

    Finding Maximum Height of Two Simultaneously Launched Balls

    This problem has been giving me problems for the past two days and I can't figure it out :( please help. this is my first ever physics class. Homework Statement A rubber ball is shot straight up from the ground with speed v_0. Simultaneously, a second rubber ball at height h directly above the...
  39. A

    Master Kinematic Equations for Physics Problem Solving | Step-by-Step Guide

    Hey guys! New to the forum! :) Anyways, so in Physics class my teacher gave us these three equations on Kinematics. He says that "pretty much everything can be done with these three", and here they are: V(final)= V(0) + AT V(final)^2= V(initial)^2 + 2A(ΔX) and... X(final) - X(initial)=...
  40. L

    Newtons Law Problem involving kinematic equation

    Homework Statement A duck has a mass of 3.0 kg. As the duck paddles, a force of 0.06 N acts on it in a direction due east. In addition, the current of the water exerts a force of 0.13 N in a direction of 60° south of east. When these forces begin to act, the velocity of the duck is 0.12 m/s...
  41. K

    Murder Mystery Solution using Kinematic Equations

    I'm new to this site, so let me know if I'm doing anything wrong. Homework Statement I have attached the original problem in a PDF file. I have to read a murder mystery story and pull information from it to plug into kinematic equations and find out who commited the murder. Important...
  42. R

    2-d kinematic w/non-constant acceleration

    Homework Statement I'm not sure how to set up the differential equation. I've got 2 point charges...both positive. One charge is fixed in position (0, -250m)...the other is traveling at an initial speed in the -x direction (10,000m, 0) with 0 acceleration. At time t=0, I calculated the...
  43. R

    How Do Forces Affect Motion in 2D Kinematics?

    Homework Statement Lets say I have a .5kg mass traveling at 1200 m/s in the -x direction with 0 acceleration. The force applied to this mass is (2.3i + .093j)N. I have to find position, velocity, and acceleration at say 1 second after the force is applied. No gravitational force involved...
  44. QuarkCharmer

    Solve 1-D Kinematic Flea Jump Problem

    Homework Statement If a flea can jump straight up to a height of 0.510 m, what is its initial speed as it leaves the ground? How long is it in the air? Homework Equations The four kinematics equations with constant acceleration I think. The Attempt at a Solution I let the positive...
  45. T

    Looking for Kinematic practice problems with solutions

    Forgive me if this is the wrong forum for this. I'm looking for practice Kinematic problems with solutions. I've looked here (http://www.physicsclassroom.com/class/1dkin/U1L6d.cfm), but those questions are too basic. My prof asks more complex problems and I'm having a hard time finding good...
  46. V

    Kinematic Problem: Calculating Acceleration & Velocity

    Homework Statement A car moves from west to east with a velocity v = 90 km / h on a straight stretch of 5km, then meets a curve to the north with 60 ° angular width and radius of curvature of r = 2Km that runs with constant angular acceleration of 3 rad / (s ^ 2). calculate the instantaneous...
  47. D

    Kinematic viscosity confusion

    Fluids with a relatively high viscosity have a high resistance to flow. Fluids with a relatively low viscosity have very little resistance to flow. Kinematic viscosity is measured in mm2/s. (This is area per second.) If one "thick" oil and one "thin" oil are poured down onto a flat plane...
  48. N

    Kinematic question from giancoli

    Homework Statement Suppose you adjust your garden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (the hose is 1.5 m off the ground). When you quickly move the nozzle from the vertical you hear the water striking the ground...
  49. R

    Solving Kinematics: Finding Release Height Above Window

    Homework Statement A water balloon takes .22 s to cross the 130 cm high window, from what height above the top of the window was it dropped? The Attempt at a Solution I'm using: v^2 = vo^2 + 2a(x - xo) v = distance/time v = 1.30 m / .22 s = 5.91 m/s (5.91 m/s)^2 = 0 +...
  50. C

    Kinematic Equations, solving a quadratic gives two solutions?

    Homework Statement Hello, after searching the internet I found this very active community and hope you can help me with my problem. On the Khan Academy website (Which I highly recommend) there are exercises such as Kinematic Equations. I was asked to solve Vi (Initial velocity) so I used the...
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