Give qualitative definition of force on the basis of Newton's first law of motion.

Name the factor on which inertia of a body depends and state how it depends on the factor stated by you.

Give one example of each of the following —
(a) Inertia of rest, and (b) inertia of motion.

An aeroplane is moving uniformly at a constant height under the action of two forces (i) upward force (lift) and (ii) downward force (weight). What is the net force on the aeroplane.