Transcript Newton`s Law of Motion.

Newton’s Law of Motion.
What is inertia?
Inertia is the idea that an object keeps moving
unless acted upon by an outside force. Much
of the initial work written about inertia was
done by Isaac Newton in the 17th century and
became known as his first law of motion. It is
one of the basic principles of physics and has
a number of real-life applications.
• The law states that if the forces acting upon an
object are balanced, then the acceleration of
that object will be 0 m/s/s.
• Objects at equilibrium (the condition in which
all forces balance) will not accelerate.
• According to Newton, an object will only
accelerate if there is a net or unbalanced force
acting upon it. The presence of an unbalanced
force will accelerate an object - changing
either its speed, its direction, or both its speed
and direction.
• Inertia is a reason why a ball that is thrown
up in the air doesn't keep flying forever.
• It helps to explain why brakes use friction
to help slow down a bike
• why an apple falling from a tree is
stopped when it hits the ground.
• Newton's second law of motion pertains to the
behavior of objects for which all existing forces
are not balanced.
• The second law states that the acceleration of
an object is dependent upon two variables - the
net force acting upon the object and the mass of
the object
• F=mxa
(the net force is the vector sum of all the forces)
• unit of force is Newton
• 1Newton = Kg.m/s2
Check Your Understanding
1. Determine the accelerations which result
when a 12-N net force is applied to a 3-kg
object and then to a 6-kg object.
2. A net force of 15 N is exerted on an
encyclopedia to cause it to accelerate at a rate
of 5 m/s2. Determine the mass of the
encyclopedia.
Newton’s third Law
• For every action, there is an equal and
opposite reaction.
• When you sit in your chair, your body exerts a
downward force on the chair and the chair
exerts an upward force on your body. There
are two forces resulting from this interaction a force on the chair and a force on your body.
These two forces are called action and
reaction forces