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. K

    How Does Particle P Chase Particle Q on a Circular Path?

    Homework Statement Starting from the center of a circular path of radius R, a particle P chases another particle Q that is moving with a uniform speed v on the circular path. The chaser P moves with a constant speed u and always remains collinear with the centre and location of the chased Q...
  2. J

    Kinematics : Relation between the velocities of 3 particles

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] Apologies for a bit hazy picture .Let the three particles be in a line after time 't' . If the inclined line (path of v) from the origin is perpendicular to the hypotenuse then we could write vt= v1cos45°t = v2cos45°t . But...
  3. Eyris

    Kinematics on a frictionless incline plane

    The situation: The mass is pushed up an incline with an angle of 1 degree with an initial velocity of 1 m/s, and it comes back down to its original position. The questions to answer: What is the total distance the object travels on the frictionless inclined plane? How long will the object...
  4. K

    Scattering angle in relativistic kinematics

    Homework Statement Considering 2 scattering particles with momenta ##p_{1}, p_{2}##, where ##p_{2} = 0## in the Lab reference. The momenta of these 2 particles after elastic collision are ##p_{1}', p_{2}'##, respectively. Due to the 4-momentum relation, we have ##p_{1i}p_{1}^{'i} = e_{1}e_{1}'...
  5. C

    1-D Kinematics Problem (Running to catch up to a bus)

    Homework Statement A person runs at a constant speed of 4.0 m/s to catch a stationary bus. When she is 6.0m behind it (t=0s), the bus leaves, accelerating with a (constant) acceleration of 1.2 m/s^2. How long does it take her to catch up to the bus? Homework Equations X = Xo + Vot + 0.5at^2...
  6. C

    Kinematics Problem Help (accident-avoidance systems for oil tankers)

    Homework Statement Because of your technical background, you have been given a job as a student assistant in a university research laboratory that has been investigating possible accident-avoidance systems for oil tankers. Your group is concerned about oil spills in the North Atlantic caused by...
  7. 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...
  8. Uriah Graves

    Finding constant acceleration without time

    Homework Statement [/B] An X-ray tube gives electrons constant acceleration over a distance of 14 cm . If their final speed is 1.0×107 m/s , what are the electrons' acceleration? Express your answer to two significant figures and include the appropriate units. Homework Equations My prof. has...
  9. P

    Kinematics -- flying a plane in the wind to a destination

    Homework Statement A plane is taking off from an airport directly west of the airport it wishes to touch down in. The plane in still air can travel with a constant speed of 730 km/h. If a wind is blowing constantly at 92 km/h [45° S of E], at what angle must the plane fly to compensate for the...
  10. A

    Quick Question about Pendulum Graphs

    Hi everyone. I just have a very quick question regarding position time graphs and velocity time graphs for a pendulum. As we know, at the maximum displacement, the acceleration is at its maximum and the velocity is zero, and vice versa when the displacement is zero. When we put this...
  11. Abhimessi10

    Difference between relative velocity and effective velocity

    Can anyone tell me the difference between concept of relative velocity and effective velocity and when to use the concept of relative velocity? For example, if a guy throws a ball from a moving object at an angle theta it undergoes projectile motion we write horizontal velocity as...
  12. C

    B How do you calculate how much force is applied to a thrown bal

    I’m trying to calculate how hard someone throws a ball. I know that F=ma, but the only force acting on a ball is the force of gravity and so the equation simply cancels out.
  13. kandelabr

    Trajectory with minimum acceleration

    Currently design of turbomachinery (impellers/turbines) is more a form of art than an engineering process. One has to guess a bunch of parameters and check if they are right in much later stages of design. I was thinking about designing the other way: we know the initial and the final velocity...
  14. T

    Is the velocity of this object increasing or decreasing?

    Homework Statement Hi everyone, 8th grade physics teacher here. We are doing a handout where we have to identify time-velocity graphs with descriptions. Can you help me with this one? https://imgur.com/a/vEIkg A) The velocity is increasing at a uniform rate. B) The velocity is decreasing at...
  15. E

    Circular motion and Kinematics

    Homework Statement l=2m b=1.5m The mass of the chair is 5kg. A boy with a mass of 50kg sits on the chair. The distance of the chair from the pole is 3m, and it spins around it horizontally with a radial velocity of 1.95 rad/s. The boy drops a ball at some moment, what would be its distance...
  16. Spoti112

    Kinematics problem with differential equations.

    Homework Statement Suppose the acceleration of a particle is a function of x, where a(x)=(2.0 s-2)*x. (a) If the velocity is zero when x= 1.0 m, what is the speed when x=3.0 m? (b) How long does it take the particle to travel from x=1.0 m to x=3.0 m. a(x)=(2.0 s-2) * x (a) V(x=3) = ? , V(x=1)...
  17. M

    Kinematics question -- Impulse applied to a plate hanging from a wall

    Homework Statement A circular plate with radius 0.5 m and mas 5 kg is hung on the wall, fixed at a point that is 0.3 m above its center. The plate can freely rotate about the fixed point with no friction. A very short-duration impulse of 5Ns, along a direction that is tangential to the...
  18. M

    Kinematics question(angular velocity)

    Homework Statement Question: A circular cylinder with mass of 1 kg and radius a=0.1 m is rotating about its cylindrical axis at a rate of 5 revolutions per second. It is then placed on a flat surface. Assuming that there is no dissipation at contact and the cylinder is rolling without slipping...
  19. Spoti112

    Kinematics, One Dimension, Acceleration, 2 objects problem

    Homework Statement Ball A is dropped from the top of a building of height h at the same instant that ball B is thrown vertically upward from the ground. At what height will the balls collide if the collision occurs when the balls are moving in the same direction and the speed of A is 4 times...
  20. N

    Simple Kinematics Problem, unsure of my error

    Homework Statement Object launched vertically with v initial =20 m/s. No air resistance. How long does it take to reach its max height? Homework Equations 1/2 at^2 + vot = dy .5mv^2=mgh The Attempt at a Solution I began by using conservation of energy to find the max height. .5mv^2 = mgh...
  21. hellovenus

    Two blocks slide on an inclined plane

    Homework Statement Two blocks slide on an incline of angle \theta . Block 1 has mass m1 and coefficient of kinetic friction μ1 with the surface, block 2 has mass m2 and coefficient of kinetic friction μ2. The gravitational acceleration is g. In terms of these parameters, under what condition...
  22. Ofir12

    Kinematics question using vectors

    A child is in danger of drowning in the river. The river has a current of 2.5 km/hr . The child is 0.6 km from the shore. A rescue boat with speed 20.0 km/hr (with respect to the water) ,located 0.8km downstream, sets off from the shore. What would be the optimum angle (shore -> boat ) to reach...
  23. T

    What does time=0 represent in kinematics

    So basically i am confused about time 0 in terms of kinamatics graphs Lets say i throw a ball upwards so what does time t=0 represent, the time after which the ball is released or the time at which ball is about to be released? Secondly in projectile motion if i throw a ball horizontally at a...
  24. S

    Kinematics question: free-fall distance traveled during a given second

    Homework Statement An object is released from rest in the gravitational field of the Earth. Air resistance is negligible. How far does the object move during the fourth second of its motion? A. 15 m B. 25 m C. 35 m D. 45 m Homework Equations v = u + at s = ut + 1/2 at^2 v^2=u^+2as...
  25. M

    Mass and kinematics -- motion of objects in a gravitational field

    does mass affect the motion of the vertical upward, vertical motion down, free fall motion, and parabolic motion?
  26. S

    Two cars driving toward each other (non-uniform speed)

    Homework Statement Two cars are 1.4 km apart and driving towards each other. One car starts from rest and accelerates uniformly at 1.2 m/s^2. The other car is driving at a constant speed of 18 m/s. When will the cars meet? Homework Equations d=vt d=ut + 1/2at^2 d=vt-1/2at^2 v^2 = u^2 + 2ad...
  27. D

    Kinematics Involving Ball, What did I do wrong?

    Homework Statement Your cousin has built a model rocket that she wishes to launch in your backyard. You're a little worried by this, and ask her for details. She tells you, when I launch the rocket straight upwards, the acceleration will be 3.5g = (3.5*9.8m/s^2) for 4.3 seconds, then burn out...
  28. 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...
  29. J

    How do I calculate the mass of a moving object?

    Homework Statement Someone mistakenly threw away a lovely couch, and you decide to take it back to your apartment. You push it with a force of 350 Newtons and at 30 degrees below the horizontal at 2 m/s. The coefficents of friction are μs = 0.4 and μf = 0.3. What is the couch's mass? Homework...
  30. michaelgtozer

    Kinematics Question -- Two motorbikes accelerating at each other....

    Homework Statement Two stationary motorbikes at time 0s are separated by distance of 80m. Both motorbikes accelerate at a constant rate as the travel towards each other. Motorbike X accelerates at a rate of 4.6m/s2 . Motorbike Y accelerates at a rate of 2.4m/s2 . Calculate the amount of time...
  31. Poetria

    How Do You Calculate the Magnitude of Acceleration in an Elevator?

    Homework Statement A person is standing on an elevator initially at rest at the first floor of a high building. The elevator then begins to ascend to the sixth floor, which is a known distance h above the starting point. A plot of the acceleration as a function of time is shown in the figure...
  32. A

    Obtaining Acceleration from Position vs Time graph

    I have collected data on a car accelerating down a straight track. I graphed it Position vs Time. Then I found the tangent slope at 5 points along the curve and plotted them as velocity. But then I linearized the position vs Time graph (position vs Time^2.) However, the slope of the velocity vs...
  33. O

    Distance of two moving particles

    Homework Statement There are two particles. There are moving equally on two intersecting lines to intersection. On time t=0 is the distance of two particles d. The velocity of one particle relative to the other has a projection u in the direcion of d. In direction perpendicular to d is the...
  34. Alexanddros81

    A child slides down the helical water slide AB (Polar Coordinates)

    Homework Statement 13.43 A child slides down the helical water slide AB. The description of motion in cylindrical coordinates is ##R=4m##, ##θ=ω^2t^2## and ##z=h[1-(\frac {ω^2t^2} {π})]##, where h=3m and ω=0.75rad/s. Compute the magnitudes of the velocity vector and acceleration vector when...
  35. P

    AP PHYSICS 1 Kinematics falling with deceleration

    Homework Statement Captain American bails out of an airplane and falls 50 meters without friction. When the parachute opens, he decelerate at 2.0m/s2. He reaches the ground with a speed of 3.0 meters/sec. a.) How long is captain america in the air? do= d= vo= v=3m/s t= ? a= -9.8m/s2 ?? (this...
  36. P

    AP Physics 1 kinematics problem

    Homework Statement The engineer of a passenger train rounding a curve at 30m/s sights a slow-moving freight train 200m ahead on the same track traveling in the same direction with a constant velocity of 10m/s. The engineer of the passenger train immediately applies the brakes, causing a...
  37. P

    AP Physics 1 Kinematics problem

    Homework Statement Luke Skywalker is making a diving run at the Death Star, approaching in his X-Wing at a rate of 500m/s. (The Death star is hollow, so it has almost no gravity.) Suddenly, at 800 meters from the Death Star, Luke fires his retro rockets. This creates a reverse acceleration of...
  38. Alexanddros81

    Cloverleaf highway interchange - determine car acceleration

    Homework Statement 13.34 The curved portion of the cloverleaf highway interchange is defined by ##R^2=b^2sin2θ##, 0<=θ<=90deg. If a car travels along the curve at the constant speed v0, determine its acceleration at A Homework EquationsThe Attempt at a Solution [/B] Is this wrong?
  39. Alexanddros81

    Determine the angular speed ##\dotθ## of the arm OC

    Homework Statement 13.30 The colar B slides along a guide rod that has the shape of the spiral R = bθ. A pin on the collar slides in the slotted arm OC. If the speed of the collar is constant at v0, determine the angular speed ##\dot θ## of the arm OC in terms of v0, b, and θ. Homework...
  40. Alexanddros81

    The collar B slides along a guide rod (Polar Coord.)

    Homework Statement 13.29 The colar B slides along a guide rod that has the shape of the spiral R = bθ. A pin on the collar slides in the slotted arm OC. If OC is rotating at the constant angular speed ##\dot θ = ω##, determine the magnitude of the acceleration of the collar when it is a A...
  41. Alexanddros81

    The rod OB rotates counterclockwise about O (Polar Coord.)

    Homework Statement 13.25 The rod OB rotates counterclockwise about O at the constant angular speed of 45 rev/min while the collar A slides toward B with the constant speed 0.6 m/s, measured relative to the rod. When collar A is in the position R = 0.24m, θ = 0, calculate (a) its velocity...
  42. C

    Kinematics question -- Adding and subtracting vectors

    Homework Statement If vector a is added to vector b, the result is the vector c = (7.00, 3.00). If b is subtracted from a, the result is the vector d = (−4.50, 9.25). what is the magnitude of a? what is the magnitude of b? Homework EquationsThe Attempt at a Solution a + b = (7.00, 3.00)c...
  43. A

    Change in direction of velocity

    If I'm driving a car and I have changed my dierction of motion without changing the speed, in this case how to calculate the acceleration of the car in a particular time? I'm not talking about circular motion.
  44. Alexanddros81

    A particle travels along a plane curve (Polar coordinates)

    Homework Statement 13.24 A particle travels along a plane curve. At a certain instant, the polar components of the velocity and acceleration are vR=90mm/s, vθ=60mm/s, aR=-50mm/s2, and aθ=20mm/s2. Determine the component of acceleration that is tangent to the path of the particle at this...
  45. Alexanddros81

    Pen P of the flatbed plotter traces the curve - Path Coordinates

    Homework Statement This is Pytels Dynamics 2nd edition problem 13.16 13.16. Pen P of the flatbed plotter traces the curve y=x3/80000, where x and y are measured in mm. When x=200mm, the speed of slider A is 60 mm/s. For this position, calculate (a) the speed of P; and (b) the normal component...
  46. C

    Shooting a bullet at an angle from a given height

    Homework Statement A sniper standing on a 70 meter-tall tower fires his rifle at 30 degrees upwards with the initial velocity of 1000 m/s. What is the range of the bullet and how much time will pass before it hits the ground? Assume no air-resistance. 2. The attempt at a solution I divided...
  47. Zer0

    Auto-Closing Gate (Relative Acceleration problem homework)

    1. Homework Statement It's an auto closing gate. Two parts of the gate are identical. I had given to find the time taken to close the gate. The distance to close point (P) of the gate from closed event of the gate is given as "a". Sorry for my bad English. What i need to know is how the two...
  48. Alexanddros81

    Particle motion - Path Coordinates

    Homework Statement Pytel Dynamics Problem 13.4 13.4 The particle passespoint O at the speed of 2.4 m/s. Between O and B, the speed changes at the rate of 2.2√v m/s2, where v is the speed in m/s. Determine the magnitude of the acceleration when the particle is (a) just to the left of pont A...
  49. T

    Find friction coefficient given initial and final velocity

    I am not sure how to approach a problem involving the friction coefficient when only given initial velocity, final velocity, and distance traveled. I could combine the friction and kinematic equations, but I am only familiar with doing that for one velocity... Here is the specific problem I had...
  50. S

    Can we say Angular Velocity is a 'moment' of tangential velocity?

    If a rigid link pin joint-fixed on ground and is rotating freely about the same point with uniform ang. vel., can we say the vector form of angular vel. (omega) is nothing but moment of the tangential (perpendicular) vel. at the other end?
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