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FORCES

FORCES. Kinematics. The study of how objects move. Dynamics. The study why objects move as they do. Kinds of Forces. Gravitational Force:.

maris-holcomb
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FORCES

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  1. FORCES

  2. Kinematics The study ofhowobjects move Dynamics The study why objects move as they do.

  3. Kinds of Forces Gravitational Force: Attractive force that exists between all objects. The gravitational force between the Earth and the moon keeps the moon in orbit. It may be the most evident but it is the weakest of all the forces. Electromagnetic Force: Charged particles at rest or in motion exert electric forces on each other. They give materials their strength, their ability to bend, squeeze, stretch or shatter. When charged particles are in motion they produce magnetic forces on each other. Electric and magnetic forces are both considered to be aspects of this single force.

  4. Kinds of Forces Strong Nuclear Force: A strong force that holds the particles of the nucleus of an atom together. Short range attractive force that is much larger in magnitude to the gravitational or the electromagnetic forces. Weak Force: Force involved in transmutation of particles within the nucleus. Only observed/viewed in radioactive decay. Stronger only than the gravitational force.

  5. History Lesson Aristotle (384-322 B.C.) Two Types of Motion Greek Philosopher and scientist, student of Plato and the tutor of Alexander the Great. • Natural Motion • Objects seek their natural resting places • - Boulders fall, Smoke rises • Heavenly bodies move in perfect circles around the Earth Worked for 2000 years Violent Motion Imposed Force Some external cause i.e.. Wind on a ship First to state that a force causes motion If an object is in motion “Against its nature” then some kind of force is responsible Earth not moving, is in its natural resting place

  6. Nikolaus Copernicus (1473-1543) Polish Astronomer who demonstrated that the Earth rotates on its axis and that the planets revolve around the sun Heliocentrist – Belief in the sun centered model of the solar system. Prior belief was the geocentric model, with the Earth as the center of the universe Received his publication “ De Revolutionibus” the day he died May 24th 1543

  7. Galileo Galilei (1564-1642) Italian astronomer, physicist, mathematician, and inventor Tried and convicted of heresy for his beliefs in the Heliocentric- Copernican model of the solar system First to define a FORCE as a Push or Pull Force is not necessary to keep an object in motion FRICTION So why do objects come to rest? Friction is a type of force, caused by irregularities in the surface of objects that are in contact. When friction is present a continual contact force is needed to keep an object in motion. Galileo believed and showed that “Experiment” not “Logic” was the best test of knowledge Galileo’s ideas discredited Aristotle and many ancient philosophies He died the year that Newton was born 1642

  8. Sir Isaac Newton (1642-1727) It was during this time that he devised a number of scientific principles that we still adhere to today A family friend recognized his intelligence and helped him to get into Trinity College, Cambridge University Born in England on Christmas day 1642 Never knew his father, As a young lad lived with his mother on their family farm In 1665 the Bubonic Plague reached Cambridge and the University was closed Three Laws of Motion Theory on colored light Fluxions – Better known as Calculus The law of Gravity Had few friends and was not a stellar student but was very bright Newton went back to his family farm and continued to study on his own.

  9. Three Laws of Motion Newton’s First Law of Motion “Law of inertia” An object will remain in it’s state of motion unless a force acts upon it. Inertia = The reluctance of a body to change it’s state of motion. Mass is a measure of inertia A Body at rest `tends to stay at rest A Body in motion tends to stay in motion

  10. Newton’s Second Law of Motion The acceleration produced by a net force on an object is directly proportional to the magnitude of the net force (in the same direction as the net force), and is inversely proportional to the mass of the object. F a = m Acceleration= Net Force/ Mass F=ma

  11. Newton’s Third Law of Motion Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. Action – Reaction Law Force is an interaction between objects Interaction always occur in pairs Hammer & Nail The hammer exerts a force on the nail to drive it into the block. The nail must exert a force on the hammer to halt it in the process

  12. Horse and Cart If unbalanced net force is present than the cart accelerates Its actually Newton’s Second Law that determines if the cart accelerates All the forces on the cart must be identified A horse has some understanding of physics. He knows Newton’s third law. For every force applied there is an equal but opposite force. So, he knows that no matter how hard he pulls the cart, the cart will pull back on him with the same force, opposite in direction. The forces must be balanced. Hence no acceleration. So why pull? If the Horse can pull on the cart more than the friction applied between the cart and the ground, 1. The pull of the horse is only one force the cart will accelerate 2. The friction between the cart and the ground is another

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