Write and explain Newton's first law of motion.

(N/A) Galileo's law of inertia was the basis of Newton's laws of motion.
Newton's first law of motion: Every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise.
$A$ body at rest or a body moving with constant velocity both represent zero acceleration. Hence,Newton's first law can be interpreted as follows:
Force is a physical quantity which can bring a body at rest into motion and which can change the velocity of an object.
In short,the physical quantity which can produce acceleration in a body is called force.
From Newton's first law,the magnitude of force cannot be determined. This is its limitation.