Newton’s laws of motion are the three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws are treated below

(i) Newton’s First Law of Motion
Newton’s first law of motion explains what would happen to the state of motion of a body in the absence of any external force. This law states:

• An object at rest will remain at rest or of travelling at a constant velocity unless acted upon by an unbalanced external force.

Newton’s first law of motion implies that things cannot start, stop, or change direction all by themselves, and it requires some force from the outside to cause such a change. Constant velocity in the definition implies that an object moving around a curve or in a circle must have force acting on it. Newton’s first law means a force is always required to make an object:

• speed up
• slow down
• or change direction.

If an object is not doing any of these, then the object is either stationary or moving with constant speed to a specific direction.

(ii) Newton’s Second Law of Motion

Newton’s second law of motion describes what would happen to a body if it experiences an unbalanced force. This law relates the unbalanced force acting on the body, the mass of the object and the resulting acceleration. Newton’s second law states:

• The acceleration of an object is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.

The mathematical form of Newton’s second can be defined as follows:

F = ma

where F is the unbalanced force, m is mass of the object and a is the acceleration. The SI unit of acceleration is m/s/s, and that of mass is kg. Therefore, the SI unit of force is newton (N), where 1 N = 1 kgm/s².