Newton’s first law or law of inertia:
An object at rest remains at rest, or if in motion, remains in
motion at a constant velocity unless acted on by a net external force. An external force is a force
originating from outside an object rather than a force internal to an object. For instance, the
force of gravity that Earth exerts on the moon is an external force on the moon . The property of
a body to remain at rest or to remain in motion with constant velocity is called inertia. Newton’s
first law is often called the law of inertia . The inertia of an object is measured by its mass.
Example-The motion of a ball falling down through the atmosphere,
Newton’s second law of motion
Newton’s second law of motion or law of acceleration is closely related to Newton’s first law of
motion. It mathematically states the cause and effect relationship between force and changes in
motion. Newton’s second law of motion is more quantitative and is used extensively to calculate
what happens in situations involving a force. Newton’s second law states that the acceleration of
an object is directly related to the net force and inversely related to its mass.
Acceleration is a vector quantity that is defined as the rate at which an object changes its
velocity. An object is accelerating if it is changing its velocity.
Riding your bicycle is a good example of this law of motion at work. Your bicycle is the mass.
Your leg muscles pushing pushing on the pedals of your bicycle is the force.
Newton’s third law of motion
Newton third law or The law of action-reaction
His third law states that for every action (force) in nature there is an equal and opposite reaction.
In other words, if object A exerts a force on object B, then object B also exerts an equal and
opposite force on object A.
example, when you jump, your legs apply a force to the ground, and the ground applies and
equal and opposite reaction force that propels you into the air. Engineers apply Newton’s third
law when designing rockets and other projectile devices.