Introduction to Motion
* Motion is a state of an object when there is a change in the position of the object with respect to its surroundings.
* An object moving along a straight line or in a specified direction is said to have one-dimensional motion or linear motion.
* If an object moves in two directions in a given plane at the same time, then it is said to have two dimensional motion.
* When an object moves in three directions at the same time, it is said to be in three dimensional motion.
* Distance is the actual length of the path covered by a moving object irrespective of the direction in which it is moving.
* Displacement is the shortest straight distance between two points in a particular direction irrespective of the path an object takes.
* Speed is the rate of distance travelled: s = distance / time (m s -1)
* Velocity is the rate of displacement: v = displacement / time (m s -1)
* A physical quantity that has only magnitude but no direction is defined as a scalar quantity.
* A vector is a physical quantity that has both magnitude and direction.
* Acceleration is the rate of change of velocity: a = velocity / time (m s -2)
Graphical Representation of Motion
* Motion can be represented using a line graph comparing dependent quantities and a common independent quantity.
* Time is always taken as the independent variable in graphical representation of motion.
* A distance-time graph represents the change in the position of an object with time.
* A velocity-time graph represents the change in the velocity of an object with respect to time.
* The area under a velocity-time graph is equal to the magnitude of displacement of the body in a given time.
* The equations that define the relationship between velocity and acceleration of a body moving in a straight line are known as equations of motion.
* Velocity-time relation: v = u + at
* Period-time relation: s = ut + 1/2 at2
* Position-velocity relation: 2as = v2 – u2
* When an object moves in a circular path with uniform speed, subtending equal angles at the centre of the circle in equal intervals, exhibits uniform circular motion.