Fill in the blanks:
$(a)$ If a force of $10\, N$ is applied to an object and it produces an acceleration of $1\, m s^{-2}$,then the mass of the object is ...
$(b)$ According to Newton's first law of motion,no force is required to keep an object moving with ......... velocity.
$(c)$ The apparent weight of an object in a lift accelerating upwards is ......... .

(A) Given $F = 10\, N$ and $a = 1\, m s^{-2}$. Using Newton's second law,$F = ma$,we get $m = F/a = 10/1 = 10\, kg$.
$(b)$ According to Newton's first law,an object continues to move with constant velocity in the absence of an external net force.
$(c)$ When a lift accelerates upwards with acceleration $a$,the apparent weight $W' = m(g + a)$,which is greater than the actual weight $mg$.