Transcript The Nature of Force

The Nature of Force
Newton’s Laws
What is a Force?
• A force is a push or a pull.
• When one object pushes or
pulls another object, you
say that the first object is
exerting a force on the
second object.
• Forces are described not
only by how strong they are,
but also by the direction in
which they act.
Forces
• In order to create motion (or stop it ) you must
have an unbalanced force.
• Balanced forces cancel each other out. (No motion)
• When two forces act in the same direction
they add together. (creating an unbalanced force)
• When forces act in opposite directions, an
one is larger than the other, the overall
force is in the direction of the greater force.
Newton’s Laws
• Isaac Newton was an English
mathematician who discovered the three
basic laws of motion.
• His first law:
– An object at rest will stay at rest, and an object
in motion will stay in motion unless acted on
by an unbalanced force. AKA: Law of Inertia
Inertia: the tendency of an
object to resist change in its
motion.
Newton’s First Law
• The amount of inertia an object has,
depends on its mass.
• The greater the mass, the greater its
inertia.
A lot of inertia!
Very little inertia
Newton’s Second Law
• Newton’s second law of motion states that
The net force on an object is a product
of its acceleration and its mass.
• Or, an easier way to remember this is:
F =Mass x Acceleration
Newton’s Second Law
• F = M*A
Mass = 5 kg
Let’s assume that the wheels of
a 5-kg car apply 10 N of force.
The net force would equal 10
Newtons.
What is the acceleration of the car?
Newton’s Third Law
• Newton’s third law states that:
For every action, there is an equal and
opposite reaction.
Action-Reaction
Recap!
• 1. An object in motion will stay in motion, or an
object at rest will stay at rest unless acted on
by an unbalanced force.
• 2. Force = Mass x Acceleration
• 3. For every action, there is an equal and
opposite reaction.