Motion

Scalar Quantities: Physical quantities which have magnitude only and no direction are called scalar quantities.

Example: Mass, speed, volume, work, time, power, energy etc

Vector Quantities: Physical quantities which have magnitude and direction both and which obey triangle law are called vector Quantities.

Example: Displacement, velocity, acceleration, force, momentum, torque etc.

Electric current, though has a direction, is a scalar quantity because it does not obey triangle law.

Moment of inertia, pressure, refractive index, and stress are tensor quantities.

Distance: Distance is the length of actual path covered by a moving object in a given time interval.

Displacement: Shortest distance covered by a body in a definite direction is called displacement.

·         Distance is a scalar quantity whereas displacement is a vector quantity both having the same unit (metre)

·         Displacement may be positive, negative or ozro whereas distance is always positive.

·         In general,, magnitude of displacement ≤ distance

Speed: Distance travelled by the moving object in unit time interval is called speed i.e. speed = Distance/ time

It is a scalar quantity and its SI unit is metre / second (m/s).

Velocity: Velocity of a moving object is defined as the displacement of the object in unit time interval i.e. velocity = Displacement / time

It is a vector quantity and its SI unit is metre / second.

Acceleration: Acceleration of an objects is defined as the rate of change of velocity of the object i.e. acceleration = Change in Velocity/ time

It is a vector quantity and its SI units is metre / second ² (m/s²)

If velocity decreases with time then acceleration is negative and is called retardation.

Circular Motion: it an object describes a circular path (circle) its motion is called circular motion. If the object moves with uniform speed, its motion is uniform circular motion.

Uniform circular motion is an accelerated motion because the direction of velocity changes continuously.