<P> This is known as uniform motion . An object continues to do whatever it happens to be doing unless a force is exerted upon it . If it is at rest, it continues in a state of rest (demonstrated when a tablecloth is skilfully whipped from under dishes on a tabletop and the dishes remain in their initial state of rest). If an object is moving, it continues to move without turning or changing its speed . This is evident in space probes that continuously move in outer space . Changes in motion must be imposed against the tendency of an object to retain its state of motion . In the absence of net forces, a moving object tends to move along a straight line path indefinitely . </P> <P> Newton placed the first law of motion to establish frames of reference for which the other laws are applicable . The first law of motion postulates the existence of at least one frame of reference called a Newtonian or inertial reference frame, relative to which the motion of a particle not subject to forces is a straight line at a constant speed . Newton's first law is often referred to as the law of inertia . Thus, a condition necessary for the uniform motion of a particle relative to an inertial reference frame is that the total net force acting on it is zero . In this sense, the first law can be restated as: </P> <P> In every material universe, the motion of a particle in a preferential reference frame Φ is determined by the action of forces whose total vanished for all times when and only when the velocity of the particle is constant in Φ . That is, a particle initially at rest or in uniform motion in the preferential frame Φ continues in that state unless compelled by forces to change it . </P> <P> Newton's first and second laws are valid only in an inertial reference frame . Any reference frame that is in uniform motion with respect to an inertial frame is also an inertial frame, i.e. Galilean invariance or the principle of Newtonian relativity . </P>

What are the 3 laws of motion define each