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Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine [email protected] Quiz tomorrow • • • • • • • • • Covers everything up to today I would know: Order of the planets speed = distance/time acceleration = ∆velocity/time Newton’s three laws of motion force = mass*acceleration 1 km = 1,000 meters 1 kg = 1,000 grams Isaac Newton (1642-1727) • One of the most influential people in human history. • His 1687 publication of the Philosophiæ Naturalis Principia Mathematica (usually called the Principia) is considered to be among the most influential books in the history of science • The book described universal gravitation and the three laws of motion • Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws Isaac Newton • Newton built the first practical reflecting telescope and developed a theory of color based on the observation that a prism decomposes white light into many colors • In mathematics, Newton shares the credit with Gottfried Leibniz for the development of the differential and integral calculus Isaac Newton • Supposedly saw an apple fall to the ground • He then understood that gravity was universal, meaning it affected both the planets and us on Earth • Came up with 3 Laws of Motion Force • Force – anything that can cause a body to change velocity Gravity • Gravity is a natural phenomenon by which objects with mass attract one another. Newton’s st 1 Law • In the absence of a net (overall) force acting upon it, an object moves with a constant velocity • An object at rest remains at rest • An object in motion tends to remain in motion unless a force is acting upon it Why do things on Earth not remain in motion? Why do things on Earth not remain in motion? • Friction Newton’s nd 2 Law • Force = mass x acceleration • Units of Force kgm/s2 = newton Newton • A Newton is equal to the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second per second How much do you weigh? • • • • So much do you weigh Say your mass is 100 kg F = 100 kg x 9.8 m/s2 F = 980 Newtons • 9.8 m/s2 is the acceleration of gravity on Earth • This is the acceleration due to the Earth’s gravitational field F = ma • F = ma • a = F/m • m = F/a Question • If you apply the same force to two separate carts, one with a mass of 1 kg and one with a mass of 2kg. Which cart will accelerate more? Answer: • If you apply the same force to two separate carts, one with a mass of 1 kg and one with a mass of 2kg. Which cart will accelerate more? • The 1 kg cart will accelerate twice as much Newton’s rd 3 Law • For any force, there is an equal and opposite reaction force • Gravity is holding you on the ground • The ground is also pushing back up on you with the same amount of force Action and Reaction • Action: Object A exerts a force on object B • Reaction: Object B exerts a force on object A http://www.vshiksha.com/system/files/u1/pslvc6-rocket.jpg Question: • Which pulls harder, the Moon on Earth, or Earth on the Moon? Answer: • Which pulls harder, the Moon on Earth, or Earth on the Moon? • The same Question: • A bus and a bug have a collision. The force of the bus on the bug splatters all over the windshield. • Is the corresponding force on the bus greater, less, or the same? • Is the resulting deceleration of the bus greater than, less than, or the same as that of the bug? Answer: • A bus and a bug have a collision. The force of the bus on the bug splatters all over the windshield. • Is the corresponding force on the bus greater, less, or the same? • The same • Is the resulting deceleration of the bus greater than, less than, or the same as that of the bug? • Less because the masses are different (a = F/m) Activities • http://www.lth3.k12.il.us/tworivers/Pet%20Projec ts/Pam%20Winterroth/pam%20winterroth's%20fi nal%20project/Newton's%20laws%20of%20moti on%20activities%20page.html Homework • http://www.youtube.com/watch?v=DI3rPT_9rW0 Any Questions?