<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> 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 . </P> <P> 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 cannot be described as linear . </P>

Motion in a straight line at constant speed is called