# What is Kinematics dynamics: Definition and 20 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. ### Angular Acceleration when accounting n-reference frames

Hello, I understand the equation that describes the angular accelerator when 3 reference frames are involved is: Now I would like to ask what is the resulting equation when accounting more than 3 reference frames, i.e. when n-reference frames are involved. Thank you.
2. ### A greater force? (A train engine pulling two identical cars)

My choice is C, which is "equal to." Here is my reasoning: The engine pulls on car 1, so car 1 is having a force acting on it, which pulls car 1 forward. Likewise, the same amount of force is applied on car 2 by car 1 by moving forward with the same amount of force from the beginning. So it is...
3. ### Find angles such that the motion travels a specific distance

We know the time it takes the water complete the whole parabola is (sin(x) * 6.5 * 2) / 9.8. So I come up with (sin(x) * 6.5 * 2) / 9.8 * cos(x) * 6.5 = 2.5, because the x component of the velocity is the same for the whole time. But I get the results like these: x≈0.30929171+πn,1.26150461+πn...
4. ### Is the Parenago Discontinuity a real thing?

Recently I came across a discussion on a Pantheist forum concerning the movement of cooler Stars & the Parenago Discontinuity. The proposal was that this disconinuity could be used as a way of testing whether cooler Star have self determination... yeah yeah I know, I'm not asking here for a...
5. ### Pytels Dynamics 12.39: A rocket is launched vertically

Homework Statement A 2000-kg is launched vertically from the surface of the earth. The engine shuts off after providing a constant propulsive force of 60 kN for the first 20 seconds. Neglect the reduction in the mass of the rocket due to the burning of the fuel and the variation of the...
6. ### Pytels Dynamics 12.26: Block moves along the x-axis

Homework Statement A 0.1-kg block moves along the x-axis. The resultant of all forces acting on the block is F = -1.2tiN, where t is in seconds. When t=0, x=0 and v=54i m/s. Determine the distance traveled by the particle during the time interval t=0 to t=4s. Homework EquationsThe Attempt at...
7. ### Finding the wind-resistance force

Imagine such situation: There is a sniper who fires his rifle, the bullet travels at the initial speed of, say, 1400 m/s. His target is standing 2000 meters away and the wind is blowing at 30 m/s opposing the bullet's motion. Let's assume that the bullet is fired in a straight lane and it may...
8. ### Choosing different axes in the same system

Homework Statement Just doing some practice problems from past finals and I needed some help on this one. Sorry if my question doesn't exactly fit the template. 2) Relevant Equations / Information For part a) and for M_1, I drew the axes such that the x-axis points to the top right, in...
9. ### A Theory of Surfaces and Theory of Curves Relationship

Hello I am interested in the Frenet-Serret Formulas (theory of curves?) relationship to theory of surfaces. 1) Can one arrive to the Frenet-Serret Formulas starting from the theory of surfaces? Any advice on where to begin? 2) For a surface that contain a space curve: if the unit tangent...
10. ### Spring Dynamic Kinematics - acceleration

Homework Statement Homework Equations Standard physics equations before forces are introduced into kinematics The Attempt at a Solution I simply looked at Chegg and could not figure out how a = 400 - kx when logic dictates that a = 400 - kx/m , since this is possibly a sum of...
11. ### Auto track using Kinematic model

Hi, I'm trying to implement an auto track guidance system for ground vehicles (Eg Tractors), I'm using Matlab and Simulink. I'm at a point where I can calculate heading errors. I'm not too sure how to calculate the lateral errors. Also, I need help in designing the controller. I'm using...
12. ### Friction between roller coaster and track

Homework Statement A roller coaster is going down on a track (see image below, the track itself is highlighted in red) without initial velocity. What is the coefficient of friction between the roller coaster and the track? height at which the cart starts (h) = 12m weight of the car (m) = 620kg...
13. ### 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...
14. ### Forces induced by a vehicle wheel on the ground

Hi, I was wondering whether anyone can help with a question I have about the forces acting on a car wheel and the forces the wheel induces on the ground surface. The way I understand it, a car wheel traveling on a flat surface has the following forces acting on it: -vertical force due to the...
15. ### How exactly do i get fnet of the object in this question...

Homework Statement This was an example question done by my teacher but i don't understand how he got the fnet of an object like the yellow part. thanks first time using the forums sorry if i didnt tag this correctly Homework EquationsThe Attempt at a Solution
16. ### Uniform circular motion with friction

I recently took an exam in my engineering mechanics class and passed the exam except for one question. I have been trying to solve this question after the fact and determine the solution, however neither I nor several engineering tutors have had any success. The professor refuses to give...
17. ### Constraints for Linkage system

Hi guys! I have a question on applying constraint on Linkage systems. Assumed that there is a two dimensional one-bar linkage, one end can only rotate and one end is free (Such as the figure above, please neglect the damper-spring system if you want). This link can rotate only 180 degrees, not...
18. ### Mechanical Advantage of a 4-bar

Alright, the problem at a glance is rather simple: find the mechanical advantage at two given values of θ2. Given: rO2A = r2 r02C = rin rAB = r3 rO4B = r4 rO4D = rout rO2O4 = r1 θ1 = 135° Find: Mechanical advantage when θ2 is equal to 104°, and when θ2 is equal to 91°. Equations to use: Mech...
19. ### Two Cars Coming to Rest on an Incline

Homework Statement A car weighing 1940lb has lost its brakes and is unable to come to a stop. A police cruiser of 3900lb gets ahead of it so that the two cars are now bumper to bumper. The combined cars are now traveling at 60mph down a 15 degree grade slope. If the police cruiser can normally...
20. ### Rotational kinematics dynamics

Homework Statement If the melting of the polar ice caps were to raise the water level on the Earth by 10m, by how much would the say be lengthened? Assume the moment of inertia of the ice in the polar ices caps in negligible (they are very near the axis), and assume that the extra water...