Force producing a change in state of motion gives a body acceleration. A body moving, or attempting to move, over another body experiences a force opposing the motion called friction. When wires, cables, or ropes are stretched, they then in turn exert a force which is called tension.

Something is in motion if it is changing position. It could be a fast-moving airplane, a leaf swirling in the wind, or water trickling from a hose. Even your school, attached to Earth, is moving through space. When an object moves from one location to another, it is changing posi- tion.

Motion is a change in position measured by distance and time. Speed tells us the rate at which an object moves. Velocity tells us the speed and direction of a moving object. Acceleration tells us the rate at which velocity changes.

The state of motion of an object is defined by its velocity – the speed with a direction. Thus, inertia could be redefined as follows: Inertia: tendency of an object to resist changes in its velocity. Such an object will not change its state of motion (i.e., velocity) unless acted upon by an unbalanced force.

A change in either the speed of a moving body or its direction or both is referred to as a change in its state of motion. Thus, the force can change the direction of motion. For example- In a cricket match, a bowler bowls the ball towards the batsman with some velocity(u).

A change in the state of motion corresponds to either a change in the speed of the body and/ or a change in the direction of motion of the body. The change in speed could mean speeding up (acceleration) or speeding down (deceleration).

Rest and motion are relative terms. In simple terms, an object that changes its position is said to be in motion while the opposite action causes an object to be at rest.

Rest: If a body does not change its position with respect to its surroundings, the body is said to be at rest. E.g. A table lying in a room is at rest with respect to the walls of the room. Motion: A body is said to be in motion if it changes its position with respect to its surroundings.

Rest and motion are basically relative terms which are linked to each other. Rest and motion define the kinetic state of an object as to whether it is moving, changing its position with time or not. Motion represents movement while rest represents stationariness.

body at motion means the object changes its position with passage of time.ex: rotating blades of the fan,moving vehicle etc.

Kinematics is the study of motion without regard to forces that cause it; dynamics is the study of motions that result from forces.

The walls are at rest with respect to the Earth. When you are sitting in the classroom, you are also at rest with respect to the Earth, and so the walls do not seem to be moving to you.