Linear motion - wikipedia Linear motion For the class of linkages, see straight line mechanism. Part of a series of articles about Classical mechanics F → = m a → ( displaystyle ( \vec ( F ) ) = m ( \vec ( a ) ) ) Second law of motion History Timeline Branches Applied Celestial Continuum Dynamics Kinematics Kinetics Statics Statistical Fundamentals Acceleration Angular momentum Couple D'Alembert's principle Energy kinetic potential Force Frame of reference Inertial frame of reference Impulse Inertia / Moment of inertia Mass Mechanical power Mechanical work Moment Momentum Space Speed Time Torque Velocity Virtual work Formulations Newton 's laws of motion Analytical mechanics Lagrangian mechanics Hamiltonian mechanics Routhian mechanics Hamilton -- Jacobi equation Appell 's equation of motion Udwadia -- Kalaba equation Koopman -- von Neumann mechanics Core topics Damping ( ratio ) Displacement Equations of motion Euler 's laws of motion Fictitious force Friction Harmonic oscillator Inertial / Non-inertial reference frame Mechanics of planar particle motion Motion ( linear ) Newton 's law of universal gravitation Newton 's laws of motion Relative velocity Rigid body dynamics Euler 's equations Simple harmonic motion Vibration Rotation Circular motion Rotating reference frame Centripetal force Centrifugal force reactive Coriolis force Pendulum Tangential speed Rotational speed Angular acceleration / displacement / frequency / velocity Scientists Galileo Huygens Newton Kepler Horrocks Halley Euler d'Alembert Clairaut Lagrange Laplace Hamilton Poisson Daniel Bernoulli Johann Bernoulli Cauchy Linear motion ( also called rectilinear motion ) is a one - dimensional motion along a straight line, and can therefore be described mathematically using only one spatial dimension. The linear motion can be of two types : uniform linear motion with constant velocity or zero acceleration ; non uniform linear motion with variable velocity or non-zero acceleration. The motion of a particle ( a point - like object ) along a line can be described by its position x ( displaystyle x ), which varies with t ( displaystyle t ) ( time ). An example of linear motion is an athlete running 100m along a straight track. Linear motion is the most basic of all motion. According to Newton 's first law of motion, objects that do not experience any net force will continue to move in a straight line with a constant velocity until they are subjected to a net force. Under everyday circumstances, external forces such as gravity and friction can cause an object to change the direction of its motion, so that its motion can not be described as linear. One may compare linear motion to general motion. In general motion, a particle 's position and velocity are described by vectors, which have a magnitude and direction. In linear motion, the directions of all the vectors describing the system are equal and constant which means the objects move along the same axis and do not change direction. The analysis of such systems may therefore be simplified by neglecting the direction components of the vectors involved and dealing only with the magnitude. Neglecting the rotation and other motions of the Earth, an example of linear motion is the ball thrown straight up and falling back straight down. Contents 1 Displacement 2 Velocity 2.1 Average velocity 2.2 Instantaneous velocity 2.3 Speed 3 Acceleration 4 Jerk 5 Jounce 6 Equations of kinematics 7 Analogy between linear and rotational motion 8 See also 9 References 10 Further reading 11 External links Displacement Main article : Displacement ( vector ) The motion in which all the particles of a body move through the same distance in the same time is called translatory motion. There are two types of translatory motions : rectilinear motion ; curvilinear motion. Since linear motion is a motion in a single dimension, the distance traveled by an object in particular direction is the same as displacement. The SI unit of displacement is the metre. If x 1 ( displaystyle , x_ ( 1 ) ) is the initial position of an object and x 2 ( displaystyle , x_ ( 2 ) ) is the final position, then mathematically the displacement is given by : Δ x = x 2 − x 1 ( displaystyle Delta x = x_ ( 2 ) - x_ ( 1 ) ) The equivalent of displacement in rotational motion is the angular displacement θ ( displaystyle \theta ) measured in radian. The displacement of an object can not be greater than the distance because it is also a distance but the shortest one. Consider a person travelling to work daily. Overall displacement when he returns home is zero, since the person ends up back where he started, but the distance travelled is clearly not zero. Velocity Main article : velocity Velocity = displacement / time. Velocity is defined as the rate of change of displacement with respect to time. The SI unit of velocity is m s − 1 ( displaystyle ms ^ ( - 1 ) ) or metre per second. Average velocity The average velocity is the ratio of total displacement Δ x ( displaystyle Delta x ) taken over time interval Δ t ( displaystyle Delta t ). Mathematically, it is given by : v a v = Δ x Δ t = x 2 − x 1 t 2 − t 1 ( displaystyle mathbf ( v_ ( av ) ) = ( \frac ( Delta x ) ( Delta t ) ) = ( \frac ( x_ ( 2 ) - x_ ( 1 ) ) ( t_ ( 2 ) - t_ ( 1 ) ) ) ) where : t 1 ( displaystyle t_ ( 1 ) ) is the time at which the object was at position x 1 ( displaystyle x_ ( 1 ) ) t 2 ( displaystyle t_ ( 2 ) ) is the time at which the object was at position x 2 ( displaystyle x_ ( 2 ) ) Instantaneous velocity The instantaneous velocity can be found by differentiating the displacement with respect to time. v = lim Δ t → 0 Δ x Δ t ( displaystyle mathbf ( v ) = lim _ ( Delta t \to 0 ) ( Delta x over Delta t ) ) = d x d t ( displaystyle = ( \frac ( dx ) ( dt ) ) ) Speed Main article : speed Speed is the absolute value of velocity i.e. speed is always positive. The unit of speed is metre per second. If v ( displaystyle v ) is the speed then, v = v = d x d t ( displaystyle v = left mathbf ( v ) \right = left ( \frac ( dx ) ( dt ) ) \right ) The magnitude of the instantaneous velocity is the instantaneous speed. Acceleration Main article : acceleration Acceleration is defined as the rate of change of velocity with respect to time. Acceleration is the second derivative of displacement i.e. acceleration can be found by differentiating position with respect to time twice or differentiating velocity with respect to time once. The SI unit of acceleration is m s − 2 ( displaystyle ms ^ ( - 2 ) ) or metre per second squared. If a a v ( displaystyle mathbf ( a_ ( av ) ) ) is the average acceleration and Δ v = v 2 − v 1 ( displaystyle Delta mathbf ( v ) = mathbf ( v_ ( 2 ) ) - mathbf ( v_ ( 1 ) ) ) is the average velocity over the time interval Δ t ( displaystyle Delta t ) then mathematically, a a v = Δ v Δ t = v 2 − v 1 t 2 − t 1 ( displaystyle mathbf ( a_ ( av ) ) = ( \frac ( Delta mathbf ( v ) ) ( Delta t ) ) = ( \frac ( mathbf ( v_ ( 2 ) ) - mathbf ( v_ ( 1 ) ) ) ( t_ ( 2 ) - t_ ( 1 ) ) ) ) The instantaneous acceleration is the limit of the ratio Δ v ( displaystyle Delta mathbf ( v ) ) and Δ t ( displaystyle Delta t ) as Δ t ( displaystyle Delta t ) approaches zero i.e., a = lim Δ t → 0 Δ v Δ t ( displaystyle mathbf ( a ) = lim _ ( Delta t \to 0 ) ( Delta mathbf ( v ) over Delta t ) ) = d v d t = d 2 x d t 2 ( displaystyle = ( \frac ( d mathbf ( v ) ) ( dt ) ) = ( \frac ( d ^ ( 2 ) x ) ( dt ^ ( 2 ) ) ) ) Jerk Main article : jerk ( physics ) The rate of change of acceleration, the third derivative of displacement is known as jerk. The SI unit of jerk is m s − 3 ( displaystyle ms ^ ( - 3 ) ). In the UK jerk is also known as jolt. Jounce Main article : jounce The rate of change of jerk, the fourth derivative of displacement is known as jounce. The SI unit of jounce is m s − 4 ( displaystyle ms ^ ( - 4 ) ) which can be pronounced as metres per quartic second. Equations of kinematics Main article : Equations of motion In case of constant acceleration, the four physical quantities acceleration, velocity, time and displacement can be related by using the Equations of motion V f = V i + a t ( displaystyle mathbf ( V_ ( f ) ) = mathbf ( V_ ( i ) ) + mathbf ( a ) mathbf ( t ) ; ! ) d = V i t + 1 2 a t 2 ( displaystyle mathbf ( d ) = mathbf ( V_ ( i ) ) mathbf ( t ) + ( \begin ( matrix ) ( \frac ( 1 ) ( 2 ) ) end ( matrix ) ) mathbf ( a ) mathbf ( t ) ^ ( 2 ) ) V f 2 = V i 2 + 2 a d ( displaystyle ( mathbf ( V_ ( f ) ) ) ^ ( 2 ) = ( mathbf ( V_ ( i ) ) ) ^ ( 2 ) + 2 ( mathbf ( a ) ) mathbf ( d ) ) d = 1 2 ( V f + V i ) t ( displaystyle mathbf ( d ) = ( \tfrac ( 1 ) ( 2 ) ) left ( mathbf ( V_ ( f ) ) + mathbf ( V_ ( i ) ) \right ) mathbf ( t ) ) here, V i ( displaystyle mathbf ( V_ ( i ) ) ) is the initial velocity V f ( displaystyle mathbf ( V_ ( f ) ) ) is the final velocity a ( displaystyle mathbf ( a ) ) is the acceleration d ( displaystyle mathbf ( d ) ) is the displacement t ( displaystyle mathbf ( t ) ) is the time These relationships can be demonstrated graphically. The gradient of a line on a displacement time graph represents the velocity. The gradient of the velocity time graph gives the acceleration while the area under the velocity time graph gives the displacement. The area under an acceleration time graph gives the change in velocity. Analogy between linear and rotational motion See also : List of equations in classical mechanics § Equations of motion ( constant acceleration ) The following table refers to rotation of a rigid body about a fixed axis : s ( displaystyle mathbf ( s ) ) is arclength, r ( displaystyle mathbf ( r ) ) is the distance from the axis to any point, and a t ( displaystyle mathbf ( a ) _ ( mathbf ( t ) ) ) is the tangential acceleration, which is the component of the acceleration that is parallel to the motion. In contrast, the centripetal acceleration, a c = v 2 / r = ω 2 r ( displaystyle mathbf ( a ) _ ( mathbf ( c ) ) = v ^ ( 2 ) / r = omega ^ ( 2 ) r ), is perpendicular to the motion. The component of the force parallel to the motion, or equivalently, perpendicular to the line connecting the point of application to the axis is F ⊥ ( displaystyle mathbf ( F ) _ ( perp ) ). The sum is over j = 1 t o N ( displaystyle mathbf ( j ) = 1 mathbf ( to ) \N ) particles and / or points of application. Analogy between Linear Motion and Rotational motion Linear motion Rotational motion Defining equation Displacement = x ( displaystyle mathbf ( x ) ) Angular displacement = θ ( displaystyle \theta ) θ = s / r ( displaystyle \theta = mathbf ( s ) / mathbf ( r ) ) Velocity = v ( displaystyle mathbf ( v ) ) Angular velocity = ω ( displaystyle omega ) ω = v / r ( displaystyle omega = mathbf ( v ) / mathbf ( r ) ) Acceleration = a ( displaystyle mathbf ( a ) ) Angular acceleration = α ( displaystyle alpha ) α = a t / r ( displaystyle alpha = mathbf ( a_ ( mathbf ( t ) ) ) / mathbf ( r ) ) Mass = m ( displaystyle mathbf ( m ) ) Moment of Inertia = I ( displaystyle mathbf ( I ) ) I = ∑ m j r j 2 ( displaystyle mathbf ( I ) = sum mathbf ( m_ ( j ) ) mathbf ( r_ ( j ) ) ^ ( 2 ) ) Force = F = m a ( displaystyle mathbf ( F ) = mathbf ( m ) mathbf ( a ) ) Torque = τ = I α ( displaystyle \tau = mathbf ( I ) alpha ) τ = ∑ r j F ⊥ j ( displaystyle \tau = sum mathbf ( r_ ( j ) ) mathbf ( F ) _ ( perp ) mathbf ( _ ( j ) ) ) Momentum = p = m v ( displaystyle mathbf ( p ) = mathbf ( m ) mathbf ( v ) ) Angular momentum = L = I ω ( displaystyle mathbf ( L ) = mathbf ( I ) omega ) L = ∑ r j p j ( displaystyle mathbf ( L ) = sum mathbf ( r_ ( j ) ) mathbf ( p ) mathbf ( _ ( j ) ) ) Kinetic energy = 1 2 m v 2 ( displaystyle ( \frac ( 1 ) ( 2 ) ) mathbf ( m ) mathbf ( v ) ^ ( 2 ) ) Kinetic energy = 1 2 I ω 2 ( displaystyle ( \frac ( 1 ) ( 2 ) ) mathbf ( I ) omega ^ ( 2 ) ) 1 2 ∑ m j v 2 = 1 2 ∑ m j r j 2 ω 2 ( displaystyle ( \frac ( 1 ) ( 2 ) ) sum mathbf ( m_ ( j ) ) mathbf ( v ) ^ ( 2 ) = ( \frac ( 1 ) ( 2 ) ) sum mathbf ( m_ ( j ) ) mathbf ( r_ ( j ) ) ^ ( 2 ) omega ^ ( 2 ) ) The following table shows the analogy in derived SI units : hide Classical mechanics SI units Linear / translational quantities Angular / rotational quantities Dimensions Dimensions time : t s absement : A ms time : t s distance : d, position : r, s, x, displacement m area : A m angle : θ, angular displacement : θ rad solid angle : Ω rad, sr frequency : f s, Hz speed : v, velocity : v ms kinematic viscosity : ν, specific angular momentum : h m s frequency : f s, Hz angular speed : ω, angular velocity : ω rad s acceleration : a ms angular acceleration : α rad s jerk : j ms angular jerk : ζ rad s mass : m kg ML moment of inertia : I kg m MT momentum : p, impulse : J kg m s, N s action : S, actergy : א kg m s, J s ML T angular momentum : L, angular impulse : ΔL kg m s action : S, actergy : א kg m s, J s MT force : F, weight : F kg ms, N energy : E, work : W kg m s, J ML T torque : τ, moment : M kg m s, N m energy : E, work : W kg m s, J MT yank : Y kg ms, N s power : P kg m s, W ML T rotatum : P kg m s, N ms power : P kg m s, W See also Angular motion Centripetal force Inertial frame of reference Linear actuator Linear bearing Mechanics of planar particle motion Motion graphs and derivatives Reciprocating motion Rectilinear propagation Uniformly accelerated linear motion References Jump up ^ Resnick, Robert and Halliday, David ( 1966 ), Physics, Section 3 - 4 ^ Jump up to : `` Basic principles for understanding sport mechanics ''. Jump up ^ `` Motion Control Resource Info Center ''. Retrieved 19 January 2011. Jump up ^ `` Distance and Displacement ''. Jump up ^ `` SI Units ''. ^ Jump up to : `` SI Units ''. Jump up ^ `` Speed & Velocity ''. Jump up ^ `` Average speed and average velocity ''. Jump up ^ `` Average Velocity, Straight Line ''. Jump up ^ `` Speed and velocity ''. Jump up ^ `` Acceleration ''. Archived from the original on 2011 - 08 - 08. ^ Jump up to : `` What is the term used for the third derivative of position ? ''. Jump up ^ `` Equations of motion '' ( PDF ). Jump up ^ `` Description of Motion in One Dimension ''. Jump up ^ `` What is derivatives of displacement ? ''. Jump up ^ `` Linear Motion vs Rotational motion '' ( PDF ). Further reading Resnick, Robert and Halliday, David ( 1966 ), Physics, Chapter 3 ( Vol I and II, Combined edition ), Wiley International Edition, Library of Congress Catalog Card No. 66 - 11527 Tipler P.A., Mosca G., `` Physics for Scientists and Engineers '', Chapter 2 ( 5th edition ), W.H. Freeman and company : New York and Basing stoke, 2003. External links Media related to Linear movement at Wikimedia Commons Retrieved from `` https://en.wikipedia.org/w/index.php?title=Linear_motion&oldid=865841353 '' Categories : Classical mechanics Linear motion Talk Contents About Wikipedia Беларуская Bosanski Català Čeština Español Euskara فارسی Français हिन्दी Hrvatski Italiano ਪੰਜਾਬੀ Português Română Русский Shqip Slovenčina Slovenščina Suomi Türkçe Українська 13 more Edit links This page was last edited on 26 October 2018, at 14 : 41 ( UTC ). Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. 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Question: motion in a straight line at constant speed is called
Answer: uniform linear motion