Let’s look at an example to see how this statement works in determining the difference in acceleration of moving objects. Let’s say you have two toy cars which are the same in every way (including mass), and you give each a push along a uniformly smooth floor. But let’s say you give car #1 a push that is harder than car #2. The harder push causes car #1 to accelerate faster. Now let’s say you have another car, #3 which has more mass (making it heavier) than cars #1 or #2. You give cars #1 and #3 the same amount of force as you give each a push. Car #1, the lighter car, will accelerate faster.
The amount which an object accelerates depends on the mass of the object and on the size (the strength) of the unbalanced force (in this case, your push) acting upon it. According to Newton’s first law of motion, objects will move at a constant velocity unless acted upon by an outside force. Therefore, Newton’s second law of motion says that whenever you see an object accelerating, there must be an external force acting on it, and he put it in mathematical terms. We can restate the mathematical equation above to state that the unbalanced force acting upon an object is equal to the mass of the object multiplied by its acceleration. It looks like this:
Newton's Second Law
Force = Mass × Accelertation
or
Acceleration = Force ÷ Mass
