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. B

    Average Velocity for Three People's Trips

    Person A travels 10.2m/s[forward]. Person B travels 10.4m/s[forward]. Person C travels 3.51m/s[forward]. Find the average velocity for the trio.I added all 3 velocities(just the magnitudes) and divided by 3, but my answer was different from the textbook's. I got 8.0m/s[forward], but the answer...
  2. A

    Solve Kinematic Problems with Graphs?

    so this is just a general question but is it possible to solve all one dimensional motion problems by making graphs, i feel like if that's the case I wouldn't need to use the kinematic equations. I usually get caught up on problems where acceleration changes over time and I have to do...
  3. T

    Calculating Distance When Two Cars Pass on I-74: 1-D Kinematics Problem

    Homework Statement Anna is driving from Champaign to Indianapolis on I-74. She passes the Prospect Ave. exit at noon and maintains a constant speed of 75 mph for the entire trip. Chuck is driving in the opposite direction. He passes the Brownsburg, IN exit at 12:30pm and maintains a constant...
  4. Mr.Y

    Relation between Tension and net force

    I am having a lot of difficulty understanding this concept. Suppose you have two objects A,B of mass A',B' connected by a massless rope. Let K Newtons be the force applied on object A .What is now the tension along the rope ? -My reasoning: K Newtons is the force applied to the combination...
  5. C

    Discrepancy with Toricellis equation in a 2D kinematics prob

    Homework Statement A stone is thrown from a height 2.1m with an angle of 45 degrees. It fell to the ground 42 m from the throwing position, measured horizontally. Initial velocity is 19,81 m/s, flight time is 3s what is the maximum height? Homework Equations All 2D kinematics equations. The...
  6. C

    Using series in a 2D kinematics problem

    Homework Statement A ball is rolling towards a rectangular hole which is 40cm deep and 2cm wide with a velocity 1m/s. It falls through the hole, bounces off the walls a couple of times and falls down. The direction of balls motion is perpendicular to the hole (falling in it from one side)...
  7. Rations

    Solving for time given a messy displacement equation

    I'm having some trouble with this problem (adapted from K&K 1.23). Homework Statement An elevator is programmed to start from rest and accelerate according to \begin{align*} a(t) &= \frac{a_m}{2}\left[1 - \cos\left(\frac{2\pi t}{T}\right)\right] &\mbox{for }0\leq t\leq T \\ a(t) &=...
  8. D

    Calculate T for Maximum Altitude: 1D Kinematics Problem Solution

    Homework Statement [/B] During your summer internship for an aerospace company, you are asked to design a small research rocket. The rocket is to be launched from rest from the earth’'s surface and is to reach a maximum height of 990 m above the earth'’s surface. The rocket’'s engines give the...
  9. P

    Kinematics Projectile Question

    I'll admit that I'm not an undergraduate(I'm in high school), but I do have a kinematic question that I'm extremely curious about. I basically would like to ask what affects the motion of a projectile, and make it stray from its path. So if I a projectile(let's use a rocket) is flying downward...
  10. Y

    Is this a valid Kinematics Equation?

    a = dv/dt a = (d/dt)(dx/dt) dv/dt = (d/dt)(dx/dt) dv = dx/dt dx = dvdt Xf - Xi = (tf-t0)*dv Is this a valid equation? It doesn't seem right to me since if velocity change is 0, then dv = 0, meaning your change in position is 0. That shouldn't be right, as even though your velocity change is 0...
  11. Yousufshad

    Basic Kinematics problem, why my method is invalid

    Homework Statement A motorist drives along a straight road at a constant speed of 14.4m/s. Just as she passes a parked motorcycle police officer, the officer starts to accelerate at 1.8m/s^2 to overtake her. Assuming the officer maintains this acceleration, determine the time it takes the...
  12. vetgirl1990

    Calculating angle of projectile to hit target

    Homework Statement A projectile is launched from an origin (0cm,0cm) on a tilted plane. The plane makes 30 degrees with the horizontal. The launcher sends the ball with a speed of 0.2m/s. At what angle should the projectile be launched to hit the target at (0.7m,0.6m) location? Assume there...
  13. vetgirl1990

    Kinematics of a falling object to hit target

    Homework Statement An airplane flies horizontally with a speed of 300m/s at an altitude of 300m. Assume the ground is level. At what horizontal distance from a target must the pilot release a bomb as to hit the target? Answer: 2.7km Homework Equations a=v/t=d/t2 r_f = r_i + v_i*t + 1/2at2...
  14. D

    How High Above the Window Was the Flowerpot When It Fell?

    Homework Statement A flowerpot falls off a windowsill and falls past the window below. You may ignore air resistance. It takes the pot 0.420 s to pass from the top to the bottom of this window, which is 1.90 m high. Part A How far is the top of the window below the windowsill from which the...
  15. J

    How Do You Calculate the Original Mass in a Relativistic Disintegration Problem?

    Homework Statement A body at rest in a frame of reference S disintegrates into two pieces moving in opposite directions. The masses of each fragment are 3.0kg and 4.0kg and their velocities 0.8c and 0.6c, respectively. Find the mass of the body before it disintegrated. (Answer: 10kg) Homework...
  16. N

    Solving Kinematics Problem for Landslide Hazard Map

    Okay, so. I'm doing a project for an environmental geology course in which I need to create a landslide hazard map. Essentially, I have a mass of rock sliding down an inclined plane. I have calculated the kinetic energy and force of the material as it moves down, as well as the final velocity as...
  17. Ryaners

    Basic kinematics: projectile motion

    This is a really basic problem but the answers I've gotten don't match up with the back of the book. I've been over it several times & can't understand where I'm going wrong - any pointers would be much appreciated! 1. Homework Statement A physics book slides off a horizontal tabletop with a...
  18. Gbox

    Finding the diferencial function of a moving particle

    Homework Statement A particle is moving in a liquid ##a=-kv## when ##k## is a constant, if a constant force is being apply on the particle ##a=-kv+\frac{F}{m}##. 1. for the formula that's include the force, find the diferencial function where ##v## will appear in it explicitly, ad its...
  19. trinkleb

    Rotational Kinematics - angle between force and velocity

    Here is the problem I am working on. I have found answers for all of them except part (f), which is the one I need help with. I will report the answers I have so far: A classic 1957 Chevrolet Corvette of mass 1240 kg starts from rest and speeds up with a constant tangential acceleration of 2.00...
  20. S

    Rotational Kinematics Question

    Homework Statement A computer disk drive is turned on starting from rest and has constant angular acceleration. If it took 0.680s for the drive to make its second complete revolution, how long did it take to make the first complete revolution? (t=?) Homework Equations Θ=(ct^2)/2 (i think) The...
  21. C

    How Does the Jacobian Process Work in Kinematics?

    Hey guys, Im studying for an exam and don't fully understand the jacobian process. Speciffically how you can differential the middle colum with respect to theta_3. Please view attached. So from step 1 to 2. Thanks.
  22. vetgirl1990

    Meaning of y-int. on graph of acceleration vs. hanging mass

    Homework Statement In an experiment, I measured the effect of mass on the acceleration of a cart, rolling down a leveled air track. I then graphed acceleration vs. mass (m'), where: m' = m / (M+m); M = mass of the cart, m = hanging mass, which was increased with subsequent trials. Homework...
  23. vetgirl1990

    Finding launch angle from vertical and horizontal distance

    Homework Statement The mountain rescue officers trigger the avalanche by firing a gun at a distant mountain slope. The muzzle velcoity of the gun is 225m/s. The horizontal and vertical distance from the gun to the slope is x=1,072m and y=538m respectively. Find the lowest angle between the...
  24. M

    I'm curious what anyone gets for part d

    Homework Statement After a wild ride on a windsurfer, you head to a lifeguard tower to fly a kite. You stand on the tower, which is 3 meters above the ground and release your kite. You let out 10 meters of string and the kite begins moving according to the following equation: y(t) = (0.9...
  25. K

    Determining velocity for a pulley/rope system

    The Question: Using a simply pulley/rope system, a crewman on an Arctic expedition is trying to lower a 5.65-kg crate to the bottom of a steep ravine of height 23.9 meters. The 60.9-kg crewman is walking along holding the rope, being careful to lower the crate at a constant speed of 1.50 m/s...
  26. M

    Understanding distances, derivatives, and integrals help?

    Homework Statement Two railroad tracks intersect at right angles at station O. At 10AM the train A, moving west with constant speed of 50 km/h, leaves the station O. One hour later train B, moving south with the constant speed of 60 km/h, passes through the station O. Find minimum distance...
  27. tk24700

    1 dimensional kinematics with car and motorcycle

    Homework Statement Two friends agree to test their physics background in 1D motion. Steve, is a distance d ahead of Jack. Jack is driving at a constant, know velocity v0 when they start their experiment. At this moment, Steve accelerates from rest with his motorcycle in such a way that they...
  28. snowsnowrain

    Who Threw the Ball First in This Physics Puzzle?

    Homework Statement A child stands on a balcony directly above a friend 5.00 m below. Each throws a ball toward the other with the same initial speed of 10.0 m/s. If each catches a ball at the same instant, which child threw a ball first? How much later was the second ball thrown? Homework...
  29. W

    A problem on two dimensional kinematics

    Homework Statement A block is given initial velocity of 5m/s up a frictionless 20 degrees incline. How far up the incline does the block slide before coming to rest? The answer is 3.73m. I set the coordinates to be perpendicular to the plane instead of parallel to the incline. I calculated...
  30. I

    What Angle Below the Horizontal Does a Hockey Puck Hit the Ground?

    Homework Statement A hockey puck slides off the edge of a table with an initial velocity of 20 m/s. The height of the table above the ground is 2 m. At what angle below the horizontal does the puck hit the ground? Homework Equations d=Vi(t)+(1/2)at^2 a^2+b^2=c^2 The Attempt at a Solution...
  31. B

    Linear kinematics problem with limited variables.

    A rock is dropped from a cliff of height h. At the same time a rock is thrown straight up from the bottom with an initial velocity. Assuming they meet, at what time will they meet. V1 = 0 A = -9.82 Thats all you have across both rocks... is this even possible. You probably have to do some...
  32. toboldlygo

    "A woman throws a ball at a vertical wall...." Proj. Motion

    So, I've already answered parts (b) and (c), but I'm struggling with (d). Thanks in advance for any help! 1. Homework Statement "A woman throws a ball at a vertical wall d = 6.0 m away. The ball is h = 3 m above ground when it leaves the woman's hand with an initial velocity of 16 m/s at 45°...
  33. C

    Straight Line Kinematics Problem

    Homework Statement [/B] A baseball pitcher throws a ball at a speed of 47m/s. When the catcher receives the ball, he pulls his hand back through a distance of 0.035m in the process of making the catch. What was the acceleration of the ball as it was being caught, assuming the acceleration was...
  34. toboldlygo

    Instantaneous Velocity from Strobe Diagram

    Hi guys! My first post here. I've been frequenting Physics Forums and have found a wealth of information, and I'm hoping I can get some specific help about this concept. Thanks! Homework Statement "Cart A and B move along a horizontal track. The top-view strobe diagram below shows the...
  35. Dhyan Patel

    Grade 12 Kinematics Vector Problem....

    Homework Statement An airplane travels at 885 km/h [W35S]. Wind blows against the plane with a velocity of 150 km/h [E55N]. What's the displacement with direction? Homework Equations v=v1^2+v2^2sqrtThe Attempt at a Solution
  36. M

    How Long Does It Take a Ball to Hit the Ground If Thrown Downward?

    Homework Statement A ball is thrown down with an initial velocity of 2.0 m/s from a height of 1.75 m, determine how long until it hits the ground. initial velocity = 2 m/s distance = 1.75 m acceleration = 9.8 m/s2 time = ? Homework Equations d=vit+1/2a(t)2 The Attempt at a Solution 1.75=2t +...
  37. K

    Half atwood machine with accelerating pulley

    Homework Statement [/B] Consider a half-atwood machine on a cart as below, with mass m_2 attached to M via a frictionless track that keeps it pinned to M but allows it to move vertically. All surfaces (except between the wheels/ground) are frictionless, and the pulley and rope are massless. If...
  38. P

    Inverse Kinematics: Understanding the Math Behind Building Virtual Arms and Legs

    Hey guys, So, I'm new here. And I'm of 13 years of age. I am a programmer in a platform called "ROBLOX". I wanted to create my own Animator within that platform, using Inverse Kinematics. However, searching through the web, everything is just so complicated to me. I don't seem to understand the...
  39. romiomustdie

    How Do You Derive the Distance Traveled by a Projectile in a Viscous Liquid?

    i have found out the second answer of the PHYSICS problem but unable to solve the first part.i tried all possible ways.:-( ---------------------------------------------- a test projectile is fired horizontally into a viscous liquid with a velocity Vo . The retarding force is proportional to the...
  40. M

    Equations of Kinematics in 2-D/Projectile Motion

    Homework Statement A tennis ball is struck such that it leaves the racket horizontally with a speed of 28.0 m/s. The ball hits the court at a horizontal distance of 19.6 m from the racket. What is the height of the tennis ball when it leaves the racket? Homework Equations v = vo + at x =...
  41. M

    Two rocks launched up/collison (Kinematics)

    Homework Statement This is a quiz question that was given in my AP physics C class. "A rock is launched upward with a speed V0. With what velocity must a second rock be launched from the same initial position at time T later so that it hits the first rock when it has a velocity of -V0/2."...
  42. MMVS

    Kinematics question about a runner

    Homework Statement A sprinter can accelerate with constant acceleration for 3.00 s before reaching top speed. He can run the 100-meter dash in 10 s. What is his speed as he crosses the finish line? Homework Equations The Attempt at a Solution So I broken up the question into two parts, one...
  43. TheNeezoMan

    If there is no acceleration, does that mean no force?

    So last year, I was told by a friend that no Acceleration means no Force, Mathematically, this makes sense (500 Kg * 0 m/s^2 = 0 N), but intuitively, I can't wrap my head around it. Maybe this is because of language and the way we use the word force in normal conversation, but in physics it is...
  44. S

    Kinematics moving ball problem

    Homework Statement A ball moving westward at 36 m/s hits a wall and rebounds at 27 m/s, eastward. (a) What is the change Δv in the vector velocity? (This is effectively the velocity of the rebounding ball relative to an image of it passing through the wall unaffected. It’s not the same as the...
  45. S

    How Far Will the Cart Travel at Increased Speeds?

    Homework Statement A cart is initially moving at 0.5 m/s along a track. The cart comes to rest after traveling 1 m. The experiment is repeated on the same track, but now the cart is initially moving at 1 m/s. How far does the cart travel before coming to rest.[/B]Homework Equations W=ΔKE[/B]...
  46. MARK 42

    Kinematics -- Projectile motion problem

    One bullet was fired from Gun A and Gun B each at varying time interval. Both the guns are 10 meters above the ground. Calculate: a) Which gun was fired first. b) Displacement and time at which the two bullets will collide.
  47. C

    How do I solve these problems (kinematics)

    Homework Statement She drives for 40.0 min at 80.0 km/h, 10.0 min at 75.0 km/h, and 30.0 min at 45.0 km/h Determine the average speed for the trip The attempt at a solution I got 66.25khm by ((4*80)+(75)+(3*45))/8 which looks like its in the ballpark range but when I enter the answer for my...
  48. I

    Kinematics problem: x(t) --> v(t) --> a(t)

    1. Problem statement: an object moves along the x-axis so it's position at any given moment is x(t) = −t3(to the third power) + 6t − 12 m. a. what is it's velocity at any given moment b. what is it's acceleration c. at what moment does the object stopsHomework Equations s=vt+1/2at2 The Attempt...
  49. D

    How high and how fast will a 25 kg rocket fly without air resistance?

    Homework Statement A 25 kg Rocket generates 400 N of thrust. It is designed to burn its fuel for 40 seconds. If launched vertically what will its final vertical velocity be when the fuel runs out? How high can it fly? How long until it reaches the ground? Neglect mass of fuel, and air...
  50. Anama Skout

    Is Special Relativity Correct for Observer A?

    So let's say you're sitting on the ground (observer A) and there's a car or something that moves at .99c (observer B). (Of course, this is all hypothetical) Now, my interpretation goes that when A is seeing B, the information he gets is distorted, namely due to time dilation, length contraction...
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