Question

According to Newton’s first law of motion, when will an object at rest begin to move?

1.when its inertia decreases to zero
2.when an unbalanced force acts upon it
3.when the action and reaction forces are equal
4.when two equal and opposite forces act upon it

Answer 1

2. When an unbalanced force acts upon it

Think of a glass of milk resting on a table. The glass weighs a certain amount more due to the load it carries. It would be unaffected until and unbalanced force (such as a hand) carelessly knocks it over spilling the contents.

Hope this helps :)