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# Motion along a curved path is known as

### 13.4 Motion along a curve - Whitman Colleg

13.4 Motion along a curve. We have already seen that if t is time and an object's location is given by r(t), then the derivative r ′ (t) is the velocity vector v(t) . Just as v(t) is a vector describing how r(t) changes, so is v ′ (t) a vector describing how v(t) changes, namely, a(t) = v ′ (t) = r ″ (t) is the acceleration vector. When a particle moves along a curved path, it is sometimes convenient to describe its motion using coordinates other than Cartesian (x-y-z). When the path of motion is known, normal (n) and tangential (t) coordinates are often used. In the n-t coordinate system, th Curvilinear motion is defined as motion that occurs when a particle travels along a curved path. The curved path can be in two dimensions (in a plane), or in three dimensions. This type of motion is more complex than rectilinear (straight-line) motion. Three-dimensional curvilinear motion describes the most general case of motion for a particle When a particle moves along a curved path, it is sometimes convenient to describe its motion using coordinates other than Cartesian. When the path of motion is known, normal (n)and tangential (t)coordinatesare often used. In the n-t coordinate system, the origin is located ontheparticle(the origin moves with the particle) A body moves along a curved path. What is the type of motion known as - 16230151 diya9019 diya9019 30.03.2020 Physics Secondary School answered A body moves along a curved path. What is the type of motion known as 2 See answers Brainly User Brainly User Answer: hey mate here your answer: the answer is-rotational motion

### Curvilinear Motion - Real World Physics Problem

Non-uniform motion can be defined as when a given body is covering unequal distances in a set and given intervals of time. If you will represent the path of a body moving in non-uniform motion on a graph, it will be a curved line If a particle moves along a space curve, the n and t axes are defined as before. At any point, the t-axis is tangent to the path and the n-axis points toward the center of curvature. The plane containing the n and t axes is called the osculating plane. A third axis can be defined, called the binomial axis, b

Curvilinear motion occurs when the object moves along a curved path. The notion of curvilinear motion is used in the applications that are related to centripetal and centrifugal forces. For example, boomerang, roller coaster, etc. 4 5. You drew a line on a path both straight and curved at the same time! This is possible because motion is measured relative to a frame of reference. In this demonstration, there are two different frames of reference, one fixed and the other rotating. When the pencil-point motion was observed relative to Card A, its path was _____

Rectilinear Motion - The path of the motion is a straight line. Curvilinear Motion - The path of the motion is curved. A few examples of linear motion are the motion of the train, football, the motion of a car on the road, etc The motion of an object moving in a curved path is called curvilinear motion. Example: A stone thrown into the air at an angle. Curvilinear motiondescribes the motion of a moving particle that conforms to a known or fixed curve. Click to see full answe The motion of an object in a circular path is known as circular motion.A toy train moving on a circular track. Earth revolving around the sun is an example of circular motion. A bicycle or a car moving along a circular track possesses circular motion. The motion of the moon around the earth is also an example of circular motion

### a body moves along a curved path

• When a particle is thrown obliquely near the earth's surface, it moves along a curved path under constant acceleration that is directed towards the centre of the earth (we assume that the particle remains close to the surface of the earth). The path of such a particle is called a projectile and the motion is called projectile motion
• We introduce the path or arc length coordinate, s, which measures the distance traveled by the particle along the curved path. Note that for the particular case of rectilinear motion (considered in the review notes) the arc length coordinate and the coordinate, s, are the same
• The term circular is applicable to describe the motion in a curved path. The motion of any object along some circular path, covering equal distance along the circumference in the same time interval is known as the uniform circular motion. In any such motion, the speed remains constant, with constantly changing direction
• Transcribed image text: A point mass m is set in motion along the path shown by relieving a pre-tensioned spring (spring constant c, pre-tensioning force Fo). The path has a friction-free area, the exact geometry of which is not known, as well as a second, friction-prone area which runs at an angle to the horizontal and connects to the curved path at the dimensioned point

One dimensional motion is the motion of a particle moving along a straight line. Two dimensional motion A particle moving along a curved path in a plane has 2-dimensional motion. Three dimensional motion Particle moving randomly in space has 3-dimensional motion a particle moves along the curve XY equals 16 so that the y-coordinate is increasing we underline this the y-coordinate is increasing at a constant rate of 2 units per minute that means that the rate of change of Y with respect to T is equal to 2 what is the magnitude in units per minute of the particles velocity vector when the particle is at the point 4 comma 4 so when X is 4 and Y is 4 so. Exercise 13.4.1. A particle moves in a path defined by the vector-valued function ⇀ r(t) = (t2 − 3t)ˆi + (2t − 4)ˆj + (t + 2) ˆk, where t measures time in seconds and where distance is measured in feet. Find the velocity, acceleration, and speed as functions of time. Hint known motion, such as pin connections with other bodies. In this mechanism, point B is known to travel along a circular path, so aB can be expressed in terms of its normal and tangential components. Note that point B on link BC will have the same acceleration as point B on link AB

### Types of Motion: Oscillatory, Periodic, Linear & Examples

Motion along a curved path may be considered effectively one-dimensional if there is only one degree of freedom for the objects involved. A road might twist and turn and explore all sorts of directions, but the cars driving on it have only one degree of freedom — the freedom to drive in one direction or the opposite direction Plane Curvilinear Motion Motion of a particle along a curved path which lies in a single plane. For a short time during take-off and landing, planes generally follow plane curvilinear motion ME101 - Division III Kaustubh Dasgupta When a particle moves along a curved path, it may be more convenient to write the equation of motion in terms of normal and tangential coordinates. The normal direction (n) always points toward the path's center of curvature. In a circle, the center of curvature is the center of the circle In Newtonian mechanics, the centrifugal force is an inertial force (also called a fictitious or pseudo force) that appears to act on all objects when viewed in a rotating frame of reference.It is directed away from an axis which is parallel to the axis of rotation and passing through the coordinate system's origin. If the axis of rotation passes through the coordinate system's origin, the.

We follow the motion of a point using a vector r(t) whose position along a known curved path is given by the scalar function s(t) where s(t) is the arc length along the curve. We obtain the velocity v from the time rate of change of the vector r(t) following the particle dr dr ds dr v = = = s˙ (1) dt ds dt d The velocity of a particle moving on a curved path as a function of time can be written as: = () = (),with v(t) equal to the speed of travel along the path, and = () , a unit vector tangent to the path pointing in the direction of motion at the chosen moment in time. Taking into account both the changing speed v(t) and the changing direction of u t, the acceleration of a particle moving on a. Motion | Class 9 Science Chapter 8 Notes, Explanation, Video and Question Answers. Motion CBSE Class 9 Science Chapter 8 - Complete explanation and Notes of the chapter 'Motion'.. Topics covered in the lesson are Rest and Motion, Acceleration, Types of Motion, Distance Time Graphs, Scalar and Vector Quantities, Velocity Time Graphs, Distance and Displacement, Derive Three Equations of Motion. This coordinate system, which is used for motion along curved paths, is discussed in detail later in the book. Summary. Uniform circular motion is motion in a circle at constant speed. Centripetal acceleration is the acceleration a particle must have to follow a circular path. Centripetal acceleration always points toward the center of rotation.

General Curvilinear Motion Curvilinear motion is defined as motion that occurs when a particle travels along a curved path. The curved path can be in two dimensions (in a plane), or in three dimensions. This type of motion is more complex than rectilinear (straight-line) motion. Three-dimensional curvilinear motion describes the most general case of motion for a particle A particle moving along a curved path undergoes curvilinear motion. Since the motion is often three-dimensional, vectors are used to describe the motion. The position of the particle at any instant is designated by the vector r = r(t). Both the magnitude and direction of r may vary with time. A particle moves along a curve defined by the path. Centripetal force is a force responsible for keeping an object moving in a curved path. The centripetal force is caused by an object's motion around a curve or in a circular path. What is the direction of the centripetal force. The centripetal force is directed towards the center of curvature of the curved path traced by the object

### 10 Examples of Motion in Real Life - StudiousGu

1. A particle is in motion along a curved path. Then, This question has multiple correct options. A. If its speed is constant, it has no acceleration. B. lf its speed is constant, the magnitude of its acceleration at any point of its path is inversely proportional to the radius curvature of the path there. C
2. The motion along a curved path is termed as circular motion, like the orbital motion of planets, ice skater, blades of the fan, gears, amusement park rides, etc. The two fundamental concepts which are studied in circular motion are rotation and revolution
3. Types of curvilinear motion with examples - a car moving on the curved road and a ball kicked by a boy. Some other examples of curvilinear motion are: The motion of cycle while taking a turn on the road, The revolution of the earth around the sun. A path followed by a javelin thrown by an athlete, etc. Back to the top known motion, such as pin connections with other bodies. Point C, connecting link BC and the piston, moves along a straight-line path. Hence, a C is directed horizontally. In this mechanism, point B is known to travel along a circular path, so a B can be expressed in terms of its normal and tangential components Motion along a curved path is two- or three-dimensional motion, and can be described in a similar fashion to one-dimensional motion. (credit: Boris23/Wikimedia Commons) The arc of a basketball, the orbit of a satellite, a bicycle rounding a curve, a swimmer diving into a pool, blood gushing out of a wound, and a puppy chasing its tail are but a. A force that causes motion in a curved path is called a centripetal force. Uniform circular motion is an example of centripetal force in action. It can be seen in the orbit of satellites around the earth, the tension in a rope in a game of tether ball, a roller coaster loop de loop, or in a bucket swung around the body ### GRY 135 - Investigations 8A Flashcards Quizle

The time for the charged particle to go around the circular path is defined as the period, which is the same as the distance traveled (the circumference) divided by the speed. Based on this and Equation, we can derive the period of motion as. (11.4.3) T = 2 π r v = 2 π v m v q B = 2 π m q B. If the velocity is not perpendicular to the. Motion along a straight line. Distance in physics, is the length of the path (the line or curve) described by an object moving through space. Distance is independent of direction. The rate of change of displacement of a object with the passage of time is known as _____ of the object. 5.. Notice that we put direction arrows on the curve in the above example. The direction of motion along a curve may change the value of the line integral as we will see in the next section. Also note that the curve can be thought of a curve that takes us from the point $$\left( { - 2, - 1} \right)$$ to the point $$\left( {1,2} \right)$$

Motion in Space: Velocity and Acceleration Suppose a particle moves through space so that its position vector at time t is r(t). Notice from Figure 1 that, for small values of h, the vector approximates the direction of the particle moving along the curve r(t). Its magnitude measures the size of the displacement vector per unit time. Figure 3 Motion Along a Straight Line. Introduction; 3.1 Position, Displacement, and displacements can be along various paths between two points. Work Done by a Variable Force over a Curved Path An object moves along a parabolic path y = (0.5 m −1) x 2 y = (0.5 m −1).

Motion, in physics, change with time of the position or orientation of a body.Motion along a line or a curve is called translation.Motion that changes the orientation of a body is called rotation.In both cases all points in the body have the same velocity (directed speed) and the same acceleration (time rate of change of velocity). The most general kind of motion combines both translation and. For uniform circular motion, the acceleration is centripetal acceleration: a = ac. Therefore, the magnitude of centripetal force, Fc, is. F c = m a c. F c = m a c . By using the two different forms of the equation for the magnitude of centripetal acceleration, a c = v 2 / r. a c = v 2 / r and. a c = r ω 2

### What Is Motion - Definition, Types, Examples & Vide

1. NCERT Solutions For Class 9 Science Motion IN-TEXT QUESTIONS SOLVED NCERT Textbook Page- 100 Question.1. An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example. Answer. Yes, the object inspite of moving through a distance can have zero displacement. Example, if an object travels from [
2. 6.3: Uniform circular motion. As we saw in Chapter 4, uniform circular motion is defined to be motion along a circle with constant speed. This may be a good time to review Section 4.4 for the kinematics of motion along a circle. In particular, for the uniform circular motion of an object around a circle of radius R, you should recall that.
3. 19. Which of the following statements is correct? (a) Motion of soldiers on march past is a periodic motion. (b) Motion of a train along a curved track on hills is the example of curvilinear motion. (c) Every periodic motion is also a oscillatory motion. (d) Hockey player running after a ball is a combined motion
4. An object moves from point A to B along three different paths. Measure the distance travelled by object along these three paths. Fig. 9.5 In any motion, you will notice that object gets displaced while it changes its position continuously. The change in position of the object is called displacement. Basically, it is the shortest distance.
5. View Lecture 5-2 kinetics-curvelinear motion1.pdf from MECHANICAL NIA2288 at University of Leeds. NIA2288 KINETICS: CURVILINEAR MOTION DR BO LIANG E-MAIL B.LIANG@HUD.AC.UK EQUATIONS O

### What is curvilinear motion give example

1. This is the Multiples Choice Questions Part 2 of the Series in Physics as one of the General Engineering and Applied Sciences (GEAS) topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including past Board Questions in General Engineering and Applied Sciences (GEAS), Physics Books.
2. A MatrixAnimationUsingPath generates Matrix values from its PathGeometry.When used with a MatrixTransform, a MatrixAnimationUsingPath can move an object along a path. If you set the DoesRotateWithTangent property of the MatrixAnimationUsingPath to true, it also rotates the object along the curves of the path.. A PointAnimationUsingPath generates Point values from the x- and y-coordinates of.
3. Any moving object can be described using the kinematic concepts discussed in Unit 1 of The Physics Classroom.The motion of a moving object can be explained using either Newton's Laws (Unit 2 of The Physics Classroom) and vector principles (Unit 3 of The Physics Classroom) or by means of the Work-Energy Theorem (Unit 5 of The Physics Classroom).The same concepts and principles used to describe.
4. 4 Linear Motion Changing Velocity If either the speed or the direction (or both) is changing, then the velocity is changing. • Constant speed and constant velocity are not the same. • A body may move at constant speed along a curved path but it does not move with constant velocity, because its direction is changing every instant
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6. The motion in which a body moves along a circular path about a fixed point or axis without changing its position is called rotatory motion. For example, Potter's wheel and the spinning top. Question 3. Define periodic motion. Answer: The motion which repeats after a regular interval of time is called periodic motion

### How Many different Types of motion in Physics with examples

When a force ( F ) acts on a body of mass ( m ) moving at speed ( v ) in a circular path of radius ( r ) normally to the direction of its motion, The magnitude of velocity ( v ) remains constant along its path , The direction of velocity changes from one point to another on its path (ii) Motion on a level circular road. When a vehicle goes round a level curved path, it should be acted upon by a centripetal force. While negotiating the curved path, the wheels of the car have a tendency to leave the curved path and regain the straight-line path. Frictional force between the tyres and the road opposes this tendency of the wheels Add a motion path to an object. Click the object you want to animate. On the Animations tab, click Add Animation. Scroll down to Motion Paths, and pick one. Tip: If you choose the Custom path option, you will draw the path that you want the object to take. To stop drawing a custom path, press Esc Figure 6.20 The frictional force supplies the centripetal force and is numerically equal to it. Centripetal force is perpendicular to velocity and causes uniform circular motion. The larger the. the smaller the radius of curvature r and the sharper the curve. The second curve has the same v, but a larger

In order to create a motion along a path, pass an array of x, y coordinates as values into the bezier definition. The coordinates refer to points relative to the element's position, not the canvas itself. In other words, if you specify x:5, y:10, the motion will be defined from 5 to the right and 10 down from where the element is currently v is the straight line velocity of the object, tangent to the curve; R is the radius of curvature caused by the force; Circular motion from centripetal force. Summary. Centripetal force is a force acting on a moving object causing it to move in a curved path, overcoming the object's inertia. That path may be a slight curve, a circle or curved path

Kinematics of motion deals with the relative motion between the various parts of the machines without considering the forces causing the motion. read more.. This displacement can be along a straight line or a curved path. (RPM) whereas the angular velocity is the measure of the angle with respect to the time along with the direction Let's begin by graphing some examples of motion at a constant velocity. Three different curves are included on the graph to the right, each with an initial position of zero. Note first that the graphs are all straight. (Any kind of line drawn on a graph is called a curve. Even a straight line is called a curve in mathematics. The combination of both forward (linear) and rotational motion results in a path that follows a curve. What kind of curve? It depends on what we choose when we program the robot. If we specify that the linear and rotational velocities remain constant, the robot's path will lie along the arc of a circle

Instead it travels along a slightly curved path that is a bit longer. This means light from a planet on the other side of the solar system from Earth reaches us a tiny bit later than we would. The driver applies the brakes, the wheels of the car lock, and the car begins to skid to a stop. There is a backwards force upon the forward moving car and subsequently a backwards acceleration on the car. However, your body, being in motion, tends to continue in motion while the car is skidding to a stop a particle moving in the XY plane has velocity vector given by V of T is equal to all of this business and so using this notation it just means that the X component of velocity is as a function of time is 1 over T plus 7 and the Y component of velocity is a function of time is T to the fourth for time T greater than or equal to 0 at T equals 1 the particle is at the point 3 comma 4 so the. The box of negligible size is sliding down along a curved path defined by the parabola y=0.... A: Given Data y=0.4x2 x=2 m v=8 m/s dv/dt=4 m/s2 question_answe horizontal path a = v2 r W N For car to go around curve fs Static frictional force must be radial Car going around a banked corner a v Motion Top view Front view a Forces W N Case II: Banked curve horizontal path a = v2 r θ To help, the static frictional force must have a radial component At high speeds the car will slide off the top of the.

When air resistance is neglected the curved paths are parabolic in shape. Step 2 Types Of Projectile Motion. Many projectiles not only follow a vertical motion, but also follow a horizontal motion. That is, as they move upward or downward they are also moving horizontally. There are the two components of the projectile's motion - horizontal and. When the aircraft is halfway through the path animation (frame 150), it is located along the curve at a UValue of 0.5. By setting the frame number and UValue and then setting a key, you change the timing for the aircraft's motion along the path. To change the timing for the aircraft along the path Parallel transport is supposed to be the curved-space generalization of the concept of keeping the vector constant as we move it along a path; similarly for a tensor of arbitrary rank. Given a curve x (), the requirement of constancy of a tensor T along this curve in flat space is simply = = 0. We therefore define the covariant derivative.

### Projectile Motion - Definition & Formula Projectile

As stated earlier linear motion is a type of translational motion and is strictly a one-dimensional motion along a straight line. 2. Curvilinear motion. This is the motion when the body in a curved path. It is also motion in two-three dimensions. So pure translational motion does not always have to be in a straight line. This scenario is viable. A relocation of the positions of linear axes into curved tool motions is known as circular interpolation. It's alternative definition is that the commands of circular interpolation are utilized to implement the tool's motion along a circular arc to the pre-set end position. In short, it is the circular movement of the tool, which could [ The motion of a projected object in flight is known as projectile motion which is a result of 2 separate with the horizontal, a projectile will follow a curved path named Parabola. Equation of Trajectory of a projectile - a parabola. The figure below shows the vertical motion on the left and the horizontal motion along the base.. - Newton's 1st law of motion states that an object must be forced to follow a curved path. - A change of direction represents a change in velocity (a vector quantity). - Therefore, even if the magnitude of a velocity vector remains constant (10 m/s), a change in direction of the velocity vector results in acceleration  IES-35. The curve traced by a point on the circumference of a circle which rolls along the inside of affixed circle, is known as [IES-1992] (a) Epicycloid (b) hypocycloid (c) Cardiod (d) involute IES-35Ans. (b) IES-36 In the mechanism shown above, link 3 has [IES-2004] (a) Curvilinear translation and all points in it trace out identical cycloids (b) Curvilinear translation and all points in it. Its motion is known as uniformly accelerated motion. e.g. 1 Motion of a freely falling body is an example of uniformly accelerated motion (or motion of a body under the gravitational pull of the earth). e.g. 2 Motion of a bicycle going down the slope of a road when the rider is not pedaling and wind resistance is negligible. Non-uniform. JavaScript: Animating objects over a curved path Tweet 0 Shares 0 Tweets 1 Comments. The Window.requestAnimationFrame method provides a means for having the browser trigger a function for you at rapid intervals and coordinated with the browser's own refresh cycle. The concept is similar to setTimeout, only faster and smoother On a flat map the plane's flight path looks curved, but on a globe, that path is the shortest one! Light travels along a geodesic path between two points in spacetime. Far from any gravity source, the shortest distance is a straight line in three-dimensional space. Near a massive object, the shortest distance is curved in three-dimensional space motion along curve PSfrag replacements 8-axis 8-axis-axis 9-axis-axis Figure 22.8: Visualizing dynamic motion along a static curve. PSfrag replacements 8-axis 9-axis-axis Figure 22.9: Some curves that are not functions. Not every parametrized curve is the graph of a func-tion. For example, consider these possible curves in th The process of animating one or more objects moving along a defined three-dimensional path through the scene is known as path animation. The path is called a motion path, and is quite different from a motion trail, which is used to edit animations. Path animations can be created in two ways: Create a path with a curve tool or identify an existing path, and attach the object to the path

In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform, with constant angular rate of rotation (and constant speed), or non-uniform with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves circular motion of. This limits the rate of change of acceleration and deceleration (jerk) and produces smoother motion and more accurate positioning. Smoothing the beginning and end of the acceleration and deceleration phases of motion - known as an S-curve motion profile - allows acceleration to increase and decrease over time, which reduces jerk plan for the velocities along the path: thereby it is possible to slow down early enough when approaching a curve and to account for the e ects that changes in the curvature have on kinodynamics. A detailed discussion of the related work will be given in the next chapter. First, we want to motivate the use of splines for locomotion

Motion can be defined as a change in the position of a body with respect to time and another body. Motion is relative in physics. Motion and rest are fundamental ideas in physics. There is no absolute rest as all bodies in the Universe are in a perpetual state of motion. Stars, planets, constellations and even galaxies are in motion with. 4. Definition Of Projectile Motion Projectile motion is a form of motion in which an object or particle (called a projectile) is thrown near the earth's surface, and it moves along a curved path under the action of gravity only. Example: Parabolic water trajectory. 5

### Uniform Circular Motion Formula: Definition, Concepts and

The only force causing an object's circular motion is centripetal force, which is always directed toward the center of the circular path.If a car is rounding a bend, for example, the centripetal force making it move in a curve rather than a straight line is directed along the radius of the circle the car is tracing out According to Newton's first law of motion, a moving body travels along a straight path with constant speed unless it is acted on by an outside force. For circular motion to occur there must be a constant force acting on a body, pushing it toward the center of the circular path. This force is called centripetal force

### A point mass m is set in motion along the path shown

For one dimensional motion (or motion in a straight line), the position at any time can be specified by a single value, x or y, with units of distance. Positions to the right of the origin will be given a positive sign; positions to the left will be negative. Distance is the length of the path along with the object moved The ecliptic marks out the path of this motion on the sky. Credit: Wikipedia. The ecliptic is an imaginary line on the sky that marks the annual path of the sun. It is the projection of Earth's. The slider-crank mechanism, which has a well-known application in engines, is a special case of the crank-rocker mechanism. Notice that if rocker 3 in Figure 5-13a is very long, it can be replaced by a block sliding in a curved slot or guide as shown. If the length of the rocker is infinite, the guide and block are no longer curved

### What is Motion and Types of Motion - A Plus Toppe

Bezier spatial interpolation is ideal for drawing a motion path that follows a complex shape, such as a map route or the outline of a logo. Existing direction handle positions persist as you move a motion-path keyframe. The temporal interpolation applied at each keyframe controls the speed of motion along the path Tangential acceleration only occurs if the tangential velocity is changing in respect to time. To find the tangential acceleration use the equation below. (Eq 5) a t = v t d t. The second type of acceleration is normal acceleration. Normal acceleration will always occur when a particle moves through a curved path As another example consider a ball, attached to a string and whirled in a circle as shown in Fig. 2a. The tension in the string applies the centripetal force to the ball, causing it to move in a circular path. The string pulls the ball toward the center of the circle while the ball pulls outward on the string and hence on your hand in accordance with Newton's third law of action and reaction Suppose that the path is fixed, a given highway for example. Then, r OP = r OP (s) is known. Different vehicles travel at different rates - speeds, changes in speeds. Properties of the highway, a planar or space curve are distinct from the motion s(t). Ex: automobile traveling along a circular race track    It could move in a straight line or along a curved path; it could move naturally (because of the motion of other masses) or artificially (because an external force moved it). Either way, it doesn. • The Coriolis effect occurs when an object traveling in a straight path is viewed from a moving frame of reference. The moving frame of reference causes the object to appear as if it is traveling along a curved path. • The Coriolis effect becomes more extreme as you move further away from the equator toward the poles This motion is called direct motion. What distinguishes the planets from the Sun and Moon is that they will also sometimes reverse their motion, travelling from east to west relative to the stars. This reverse motion is known as retrograde motion. Retrograde motion can last from weeks (Mercury) to months (Saturn) The purpose of motion control is to move an axis, or multiple axes, to a specified position or through a predefined path. For the first case, some form of point-to-point positioning is used. For motion that must pass through a predetermined set of points, a method known as contouring is used