Chapter 5 IONS/IONIC COMPOUNDS AND NEWTON’S LAWS (FORCES)

Objectives  Describe force and give examples in nature  Apply newton’s laws to every day examples  State newton’s three laws of force  Identify the four forces found in nature

Types of Forces There are four forces of nature :  strong nuclear Force  electromagnetic force  weak nuclear force  gravity

Strong nuclear force  The strong nuclear force holds the particles of the nucleus together  strongest of the four forces  always attractive  It only acts over a very short distance, m ( m)  Ex: the parts of the nucleus, protons and neutrons, are held to together by nuclear force

Electromagnetic Force  The electromagnetic force is responsible for positive and negative charges attracting, and like charges repelling  responsible for north poles of magnets attracting south poles, and like poles repelling  Without the electromagnetic force, negative electrons would not orbit the positive nucleus  100 times weaker than the strong nuclear force

Weak Nuclear Force  involved in one of the three types of radiation, beta decay (electrons are emitted eventually changing into a different element)  thousands of times weaker than the strong force  Ex: Actinides release nuclear energy due to the splitting of their nucleus

Gravity  Gravity causes any mass to be attracted to any other mass  weakest of the four forces  always attractive  Unlike the strong nuclear force, it acts over very large distances

Mass  Mass is the amount of material (matter) in an object  unit of mass is the kilogram (kg)  If you moved an object to the moon, its mass would stay the same but its weight would change

Inertia  The property of a body to resist changes to its state of motion is called inertia.  The more inertia an object has, the more difficult it is to speed it up, slow it down, or change its direction.  (the more mass the more inertia) (less mass, less inertia)

Weight  Weight is equal to mass times the gravitational acceleration of the object’s location  Earth’s gravitational acceleration = 10m/s 2  Weight is a force, measured in Newtons (N)  If an object is moved to another planet or moon with different gravity, the weight will change

Newton’s First Law of Motion  An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.  

Newton’s Second Law of Motion  MASS RESISTS ACCELERATION:  acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.  What doe above statement really mean?  As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased.

Newton’s Third Law of Motion  For every action, there is an equal and opposite reaction.  All forces result from interactions between objects.  Forces always come in pairs.

Identifying Action and Reaction Force Pairs  Identify the action – reaction pairs 1. Action: Baseball pushes glove leftward Reaction: The glove pushes the baseball rightward 2. Action: Bowling ball pushes pin leftwards. Reaction: Pin pushes bowling ball rightward 3. Enclosed air particles push balloon wall outwards. Reaction: Balloon wall pushes enclosed air particles inwards