introduction

Q – What is periodic motion?

A – An object or a part of it repeats its motion after a fixed interval of time. This type of motion is called periodic motion.

Q – Give three examples of periodic motion.

A – (i)   Motion of a pendulum,  (ii)   a branch of a tree moving to and fro, (iii)    motion of a child on a swing,

Q – What is motion?

A – The changing in position of an object along with time is called motion.

Q – What is rectilinear motion?

A – The objects move along a straight line. This type of motion is called rectilinear motion.

Q – What is circular motion?

A – When an object moves along the circular path like a stone, the distance of the stone from your hand remains the same. Such type of motion is called circular motion. Ex. –

Q – Give two example of circular motion.

A –  (i)  The motion of a point marked on the blade of an electric fan (ii)  the hands of a clock are examples of circular motion.

Q – Define unit.

A – Measurement means the comparison of an unknown quantity with some known quantity. This known fixed quantity is called a unit.

Q – What is S. I unit ?

A – The system of units now used is known as the International System of Units (SI units).

Q – Write the SI unit of length.

A – The SI unit of length is a metre.

Q – Write the full form of S. I Unit.

A - International System of Units (SI units)