Kinematic Definition and 406 Threads

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. Emilyyyyyyyyy

    Calculate the impact force when falling from a height

    To find vx vx = dx/t = 3.86 m/1.5 s= 2.573 m/s To find Ek Ek = ½mvx²= ½(79.4)(2.573)²= 262.8 J W = FnetΔd Fnet = 262.8 J/ 3.86 m = 68 N He hits him with a force of 68N
  2. archaic

    Acceleration after applying a force

    Hello, 1) Suppose I throw a ball with a force ##F=ma##, the instant it leaves my hand, does it have the same acceleration ##a## added to it accelerations due to "ambient" forces (air resistance, gravity..)? 2) If I am right about 1), doesn't my hand already carry the acceleration/deceleration...
  3. A

    I Faking a Formula For Movement Through Gravity

    I have a strange question. It's strange because I don't need a correct answer. I need an answer that seems correct and leads to predictable results. I'm making a multiplayer computer game where the players fire cannons in outer space. The cannon shells will move through the gravitational fields...
  4. Avatrin

    Programming to learn kinematics

    Hi I am learning kinematics. Topics include inertia tensors, cosine matrices, quaternions, Euler angles etc... To learn these topics well, I want to try working on something a bit more difficult than just the underlying math. That will probably keep me more motivated. So, I am looking for...
  5. S

    Kinematic problem: velocity and stuff

    1. A stone is thrown vertically downwards from the observation deck of the CN Tower, 400 m above the ground, with a velocity of 12 m/s [down]. A) How long will it take the stone to reach the ground ? B) How fast will it be going when it hits the ground ? I just got into physics, so I’m not...
  6. D

    Max Speed to Move from Point A to Point B

    Hi, I need help with this problem: Homework Statement Condition: an object has to move from point A to point B in the least time possible. The distance between the points is L. The object can accelerate (decelerate) with a fixed acceleration ##a## or move with a constant speed. What maximum...
  7. K

    Baseball in the air 2D motion question

    Homework Statement A baseball is hit into the air, nearly vertically, with a speed of 27 m/s. When it comes down, the ballplayer catches it in his glove. Air resistance (drag) is actually fairly important for a baseball in flight, but for now let’s assume it is negligible. (a) How high does...
  8. T

    Maximizing Transferred Energy between n bodies in linear collisions

    Homework Statement My problem has two parts. 1) We have two point masses ##m,M##. and there is another mass ##m_1## between them.They are all aligned in a line. Mass ##M## is moving with speed ##u_1## toward ##m_1## and after collision and all other masses are not moving. we want to find...
  9. F

    Rigid body kinematic motion and rotation

    Hello everyone, A rigid body is a system whose points, pairwise, always keep a constant mutual distance. Let's say the body is in a certain configuration ##C_0## at time ##t_0## (which means that each point has a specific velocity and position relative to a fixed lab reference frame) and the...
  10. E

    Relationship between ln k and 1/t using different formula

    Hi, I'm currently taking Chemistry 101 and came across this equation that seems to contradict what I've learned before. I don't know the name of it, but here is the equation and its implication. Now another equation we have learned is the Arrhenius equation, which is as follows: If I...
  11. Subrahmanyan

    Electrical Help finding appropriate equipment

    I would like to measure time period of very short periods of electricity flow in the range of micro seconds or even smaller;can someone tell me me a device that can help me do this?
  12. AntSC

    Modifying Newton's Kinematic Equations for High Altitude

    I recently watched a video on youtube where a guy fires a 50 cal. rifle straight up into the air and measures the time of flight at about 100s. It got me thinking about what altitude the round reached. So I used the kinematics equations and obtained a value of 12.25km. Amazing, but I wondered...
  13. navneet9431

    Laws of motion while climbing a Rope

    I'm a little confused with the application of laws of motion on a man climbing a rope. Suppose a man of mass Mg is climbing a rope with an acceleration a. Rope is massless. Now if look through the frame of the piece of rope held by the man, there is a force Mg downward by man, ma downward...
  14. I

    Setting two expressions equal to each other

    Homework Statement Two cars are facing each other on a long straight airport runway. They are initially separated by a distance of 1 km. Car A begins to accelerate towards the other car at a uniform 0.5 ms^-2. Ten seconds later car B begins to move towards the other car with a uniform...
  15. A

    An electron & a proton are each placed in an electric field

    Homework Statement An electron and a proton are each placed at rest in an electric field of 687 N/C. What is the velocity of the electron 56.5 ns after being released? Consider the direction parallel to the field to be positive. The fundamental charge is 1.602×10−19 C, the mass of a proton is...
  16. devilish_wit

    I'm stuck This is a combination of dynamics and free fall

    Homework Statement A flat cushion of mass m is released from rest at the corner of the roof of a building, at height h. A wind blowing along the side of the building exerts a constant horizontal force of magnitude F on the cushion as it drops as shown in the figure below. The air exerts no...
  17. devilish_wit

    I have a hard time with kinematics involving inclined planes

    Homework Statement Two blocks of mass m1 = 3.00 kg and m2 = 6.00 kg are connected by a massless string that passes over a frictionless pulley (see the figure below). The inclines are frictionless. Image - https://www.webassign.net/serpse9/5-p-049.gif The inclined plane is shaped like a...
  18. C

    Raindrop free falling -- calculate the velocity and time

    Homework Statement Raindrops fall from a broken gutter at 1.0 s intervals to the ground , 19.6 m below Neglecting air resistance and taking g as 9.81 calculate the time for each drop to reach the ground velocity of the drops as they reach the ground speed of drop at the height of 14.7 m I...
  19. L

    Was the Driver Speeding Before the Crash?

    Homework Statement "Based on the following data, determine if the driver who crashed was driving over the speed limit" The relevant data given is: -A 2002 Volvo t-bones a truck in an alley with a speed limit of 20km/h -An eyewitness heard tires screech, then a loud bang, and also said the...
  20. K

    Kinematics within a simulation

    Homework Statement I'm simulating a warehouse (in Unity) where forklifts and other vehicles transport stuff from point A to point B. The routes are modeled as a graph with vertices and edges. Every transport is saved as a task in a backend system with the relevant data such as starting time...
  21. L

    I'm having a comprehension issue with a 2-D motion problem.

    1. Problem Statement A 2 kilogram block rests at the edge of a platform that is 10 meters above level ground. The block is launched horizontally from the edge of the platform with an initial speed of 3 meters per second. Air resistance is negligible. The time it will take for the block to reach...
  22. T

    Am I setting up this kinematic equation properly?

    A race car starts from rest and goes a quarter mile (1/4 mi) in 12.1 seconds. Assume the acceleration of the car is constant. (a.) What is the acceleration of the car? (b.) What is the final speed of the car? (c.) If you hit the brakes, how far would it take to stop the car if the breaks cause...
  23. V

    Find Angular Velocity for Moving Particle Parallel to x-Axis

    Homework Statement A particle is moving parallel to x-axis in the positive direction with velocity v such that at all the instants the y -axis component of its position vector is constant and is equal to 'b'. Find angular velocity about origin. Homework EquationsThe Attempt at a Solution I...
  24. Liszzy

    Useful link for kinematic topics (physics)

    https://courses.lumenlearning.com/boundless-physics/chapter/basics-of-kinematics/
  25. Cocoleia

    Position of particles on a detector after decay

    Homework Statement A hypertriton (a bound system with a L hyperon together with a deuteron core (proton and neutron) is produced at the origin of the coordinate, (x,y)=(0,0) with a velocity of 0.94c (beta=0.94), flying along the x-axis. The mass of the hypertriton is 2.991 GeV/c2 . It decays...
  26. wildonion

    Kinematic viscosity for water on Mars

    Hi - I am trying to understand the relationship between atmosphere pressure, viscosity, and density - specifically water. Is there are way to estimate a range of dynamic viscosity and density values based on varying atmospheric pressures and/or temperature that I could use on any planet. Thanks...
  27. AIshikrakshit

    Can You Solve the Problem of Projectiles with These Equations?

    Homework Statement Homework Equations $$h=ut+1/2at^2$$ $$h=x\tan\theta-1/2g\frac{x^2}{u^2\cos^2\theta}$$ The Attempt at a Solution I tried to take a random angle theta for the lower particee and then using the equation of the upper particle tried to solve them together and find condition for...
  28. D

    Kinematic equation problem -- A fountain shoots water out of the ground ....

    Homework Statement 1. A fountain shoots water out of the ground at a 40° angle. It’s horizontal velocity is 2 m/s and the water lands 3 meters away. What is the maximum height that the water reaches during that time? Homework Equations Dy =vit + ½ at2 and Vfy2 = Viy2 + 2ady The Attempt...
  29. Victoria_235

    Kinematics problem -- Calculating acceleration from the trajectory

    Homework Statement For each of the following cases, represent on the trajectory, the velocity and tangential and normal components of the acceleration at times t1 and t2 of a mobile that moves according to the graph of s (arc) versus t (time) on the left. The point O on the trajectory marks the...
  30. FelixLudi

    Solving Kinematic Movement Equation: Bike Acceleration

    Hi, It's my first post here on the forum and I'm just looking for an answer to a basic kinematic movement equation. This is the text of a problem: "A bike accelerates uniformly from rest to a speed of 7.10 m/s over a distance of 35.4 m. Determine the acceleration of the bike." Now, in the...
  31. Jenna

    Using Energy and momentum conservation to derive the equation

    Homework Statement I need to find the intial velocity of a ball, given the angle the pendulum bob swings through. I need to derive this equation. [/B] V0=4.43mtotalL1/2{1-cosΔθ}1/2/mball Homework EquationsThe Attempt at a Solution I have barely any attempts since I can't even think where to...
  32. B

    A Can KE be reformulated using |v| instead of v^2?

    While doing some calculations on v_rms using the Maxwell-Boltzmann distribution, I noticed that v_rms and v_avg are pretty similar (https://casper.berkeley.edu/astrobaki/index.php/File:MaxwellSpeedDist.png). In fact, really it's just the choice of using the 1-norm (|v|_avg) vs. 2-norm sqrt(v^2...
  33. M

    Kinematic Boundary Condition Fluids

    Hi PF! Given a fluid/fluid interface ##F(t,x,y,z) = 0## the kinematic boundary condition states ##DF/Dt = 0##. Given ##y=F## the text states ##v = \partial_tF+u\partial_xF+w\partial_zF##. How is this possible? I thought ##DF/Dt = 0 = \partial_tF+u\partial_xF+v\partial_yF+w\partial_zF## and...
  34. E

    Kinematic Equation Rearrangement

    So to an extent, I am able to rearrange simple kinematic equations; I can solve for Vi from the equation Vf = Vi +a x t, but I need some help with some other kinematic equations. For my first problem, I need to solve for a variable, (whether it be Vi, Vf, or t) from d= 1/2 (Vi+Vf) t. It seems...
  35. R

    Completely stumped on this one -- Kinematic Conceptual problem

    Homework Statement You are at a stoplight when you see a car approaching from behind at constant velocity. To avoid getting rear-ended, you accelerate forward with constant acceleration. Assume that you have managed to start at the last possible instant to avoid getting hit, as determined by...
  36. M

    Calculating the Velocity of an Elevator

    Homework Statement A teacher rides in an elevator that moves upwards at a constant velocity and holds a set keys 1.00m above the floor of the elevator. After 2.00 seconds of moving upwards from the ground level of the science building, theteacher releases the keys from their hand. Relative to...
  37. W

    Find the max speed so that an electron doesn't hit the plate

    Homework Statement An electron is fired from x = 0 with an unknown V0 at 45 degs to the horizontal between two parallel plates separated by 2 cm. Electric field is 103 j N/C. Find: a) The max value of V0 so that the electrons don’t hit the upper plate 3.75 * 106 m/sHomework Equations If you...
  38. O

    Projection at an angle - throwing stones

    Hello everyone. I have this problem: 1. The problem statement, all variables and given/known d I throw stone from height h at an angle α, then at an angle β (so I know h, α, β). I throw it with same velocity v. The stones fall in same distance d. The question is: find the d (distance) and v...
  39. R

    Kinematic problem, are my variables right,

    Homework Statement A car starts from rest at a stop sign. It accelerates at 4.3 m/s2 for 6.0 s , coasts for 2.5 s , and then slows down at a rate of 2.5 m/s2 for the next stop sign. How far are the stops signs apart. x0=0m v0=0m/s t0=0s I put 0 because it says a car stars from rest. Not sure if...
  40. P

    2-D Kinematic Velocity and Acceleration Practice Problem

    "A dog running in an open field has components of velocity vx = 1.8 m/s and vy = -1.8 m/s at time t1 = 10.8 s . For the time interval from t1 = 10.8 s to t2 = 23.2 s , the average acceleration of the dog has magnitude 0.45 m/s2 and direction 32.0 ∘ measured from the +x−axis toward the +y−axis."...
  41. J

    Constant velocity, constant acceleration?

    Homework Statement Hi, I have a quick question about an experiment I am doing. I did an experiment where I rolled a ball over a flat surface and dropped a ball from a height, and I was asked if the ball rolling over the flat surface (1-d) motion is subject to constant velocity? I was also...
  42. G

    1D Kinematics problem with a plane taking off

    Homework Statement An Airbus 380 needs to reach the velocity of 280 kmh^-1 before it takes off. The maximum acceleration the plain reaches in the runway is 0.95 ms^-2. Verify THAT the plane can use an airport with this runways. Runway 1: 3805 meters (SSW-NNE) Runway 2: 2400 meters (S-N)...
  43. Kiwigami

    Find time given a force with respect to displacement

    Homework Statement With a function that gives Force with respect to Displacement (F(x) = 2000-100x), is there a way to find a general formula for the time it takes from displacement 0 to 20? The force is acting on an object, pushing it horizontally. Assume no friction and no air resistance...
  44. Kiwigami

    Finding Velocity: F=ma or KE = 0.5mv^2

    Here is a made up function of force changing with respect to displacement: F(x) = 2000 - 100x The force is applied onto an object, pushing it horizontally. Ignore friction and air resistance. The mass is constant. I'm trying to find Velocity with respect to displacement. Attempt 1: Knowing F =...
  45. Elena14

    Air resistnce in projectile motion decreasing time of flight

    If the air resistance causes a vertical retardation of 10 percent of value of acceleration due to gravity, then the time of flight of a projectile will be decreased by nearly? Take g=10m/s^2 My attempt: Only the vertical component of the projectile will be affected by changes in g I understand...
  46. DaTario

    A Simple 1D kinematic exercises with metric tensor

    Hi All I would like to know if there is a way to produce simple one dimensional kinematic exercises with space-time metric tensor different from the Euclidean metric. Examples, if possible, are welcome. Best wishes, DaTario
  47. Aslet

    A spring-mass system in circular motion

    Homework Statement I uploaded the image of the system to have a visual example. : ) A point mass ## m ## connected to a spring is bounded to move on a circular guide with radius ## R ## without friction. The guide is fixed to a vertical plane and the other extremity of the spring is attached at...
  48. S

    Classical Hard projectile motion problem

    In the standing broad jump, one squats and then pushes off with the legs to see how far one can jump. Suppose the extension of the legs from the crouch position is 0.600 m and the acceleration achieved from this position is 1.25 times the acceleration due to gravity, g . How far can they jump...
  49. S

    Basic kinematic problem, find velocity using certain data

    Hi. Sorry, couldn't make a more specific tittle, I'm not used to solve physics problems. A friend of mine handed me the following problem: Homework Statement You have a graph that denotes the aceleration of an object as a function of the position of the object. This object has a mass of 10 Kg...
  50. Bunny-chan

    Projectiles launched at complementary angles

    Homework Statement a) Show that for a given velocity V_0 a projectile can reach the same range R from two different angles \theta = 45 + \delta and \theta = 45 - \delta, as long as R doesn't go over the maximum range R_{max} = \frac{V_0^2}{g}. Calculate \delta in function of V_0 and R. b)...
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