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Chapter 10. Section 1 - The Nature of Force. Force - a push or pull Unbalanced Forces - acting on an object will change the object’s motion Balanced Forces - acting on an object will not change the object’s motion Inertia - the tendency of an object to resist a change in it’s motion.
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Section 1 - The Nature of Force • Force - a push or pull • Unbalanced Forces - acting on an object will change the object’s motion • Balanced Forces - acting on an object will not change the object’s motion • Inertia - the tendency of an object to resist a change in it’s motion Chapter 10
Newton’s First Law of Motion • An object at rest will remain at rest, and an object that is moving at a constant velocity will continue moving at constant velocity unless acted upon by an unbalanced force. Chapter 10
Section 2 - Force, Mass and Acceleration Newton’s Second Law of Motion Force = Mass x Acceleration F=ma • Force = Newtons (N),Mass=kilograms (kg), Acceleration = m/sec2 • Mass - the amount of matter in an object (SI units = kilogram (kg)) • Sample Problems pg.321 Chapter 10
Section 3 - Friction and Gravity • Friction - The force that one surface exerts on another when the two rub against each other. • The strength of the force of friction depends on two factors: the types of surfaces involved and how hard the surfaces push together Chapter 10
Friction (cont.) • Is friction bad? ice, walking, car, bike • Types of friction • sliding friction - objects slide against each other • rolling friction - object is round or has wheels • fluid friction - object moves through fluid (swimming) Chapter 10
Gravity • The force that pulls objects toward Earth (g = -9.8m/sec2) • Free fall - only gravity acting on the object (in a vacuum) • Projectile motion - throw object horizontally (football, soccer) • Air resistance - fluid friction • Terminal velocity - greatest velocity an object in free fall can have • air resistance forces balanced with gravity Chapter 10
Gravity (cont.) • Weight - measure of the force of gravity on an object • Mass - measure of the amount of matter in an object • Weight = mass x acceleration due to gravity W=mg • Law of Universal Gravitation - The force of gravity acts between all objects in the universe. Chapter 10
Section 4 - Action and Reaction • Newton’s Third Law of Motion If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction of the first object. • Action-Reaction - Squid pg.333, skater, kick, walking • Forces cancel? Volleyball pg.334 Chapter 10
Momentum • Momentum = mass x velocity • Sample problems pg.335 • Law of Conservation of Momentum The total momentum of any group of objects remains the same unless outside forces act on the objects. • Train examples - overheads pg.337 Chapter 10
Section 5 - Orbiting Satellites • Rocket lift off - Newton’s third law - gasses expelled with a downward force, exert an equal but opposite force upward on the rocket. • Satellite - any object that travels around another object in space • centripetal force - any force that causes an object to move in a circle Chapter 10
Orbiting Satellites (cont.) • satellites in orbit around the Earth continually fall toward Earth, but because Earth is curved they travel around it pg.340 • Satellite Motion Chapter 10
force net force inertia Newton’s first law Newton’s second law Newton’s third law friction gravity momentum conservation of momentum satellite centripetal force Chapter 10 Vocabulary Chapter 10