NEWTON’S FIRST LAW OF MOTION Chapter 2

2.1 ARISTOTLE ON MOTION  Unnatural motion  Requires a force  Natural motion  Occurs without a force

2. 2 GALILEO’S CONCEPT OF INERTIA  Galileo stated that a force is required to start an object moving, but once moving, no force is required to keep it moving – except for the force to overcome friction.  Through experimentation, Galileo found that all objects show the same property of motion.

DISTANCE VS. DISPLACEMENT  Distance refers to how much ground is covered while an object is in motion.  Displacement is how far out of place an object is.

2.3 SPEED AND VELOCITY  Galileo was the first to define and measure speed.  Formula: speed = distance / time  Velocity is a vector quantity,  Formula: velocity = (distance / time) and a direction!!!

2.4 MOTION IS RELATIVE  Everything is always moving.  When discussing how any object moves we mean its motion relative to something else.  What is Lightening McQueen’s motion relative to?

2.5 NEWTON’S 1 ST LAW OF MOTION: THE LAW OF INERTIA  Every object continues in a state of rest or of uniform speed in a straight line unless acted on by a nonzero net force.  When an object is moving, it tends to remain moving, along a straight line path.

2.6 NET FORCE – THE SUM OF ALL FORCES ON AN OBJECT  A net force can change an object’s state of motion.  Net force is the total force acting on an object.  There is usually more than one force acting on an object.

2.7 EQUILIBRIUM FOR OBJECTS AT REST  When the net force on an object is zero, its state of motion does not change, and we say that the object is in mechanical equilibrium.  ΣF = 0

2.8 THE SUPPORT FORCE – WHY WE DON’T FALL THROUGH THE FLOOR  The support force (also called the normal force) is a force that cancels gravity.  Consider the book in the picture.

2.9 EQUILIBRIUM FOR MOVING OBJECTS  When an object is moving at a steady pace, without changing its state of motion the object is also said to be in equilibrium.

VOCABULARY!!!  Equilibrium rule  Force  Inertia  Net force  Newton  Newton’s First Law of Motion – The Law of Inertia  Speed  Support force  Vector quantity  Velocity  Distance  displacement