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Transcript
Chapter 13 Forces and Motion Preview Section 1 Gravity: A Force of Attraction Section 2 Gravity and Motion Section 3 Newton's Laws of Motion Concept Map < Back Next > Preview Main Quick Write Do you know of a place where gravity does not exist? If so, where? Why or why not? < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction What You Will Learn • Gravity affects all matter. • Gravity is a force. • The law of universal gravitation explains how distance, mass, and gravitational force are related. • Weight depends on gravity, but mass does not. < Back Next > Preview Main Multiple Meanings Term Common Meaning Scientific Meaning law rule from government description that predicts what will happen if something specific happens vacuum electric appliance that sucks up small things a place with no matter (objects) < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction The Effects of Gravity on Matter • Gravity is a force of attraction between objects that is due to their masses. < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction The Effects of Gravity on Matter • All matter has mass. • Gravity is a result of mass. • Therefore, all matter is affected by gravity. < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction The Effects of Gravity on Matter • Gravity between the objects of the solar system holds the solar system together. < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction The Effects of Gravity on Matter • Earth has a huge mass. Therefore, Earth has strong gravitational force. < Back Next > Preview Main Sir Isaac Newton • a British scientist • Discovered the law of universal gravitation in1665. < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Law of Universal Gravitation (Newton)-General • The same unbalanced force that affects the motion of small objects (apple) also affects the motion of larger objects (moon). • This unbalanced force = gravity. • universal = applies to all objects in the universe < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Law of Universal Gravitation (Newton)-Mass • All objects in the universe attract each other through gravitational force. • mass of objects = gravity between objects • mass of objects = gravity between objects < Back Next > Preview Main Activity: Mass Judgments < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Law of Universal Gravitation (Newton)-Distance • The force of gravity depends on the distance between two objects. • distance = force of gravity • distance = force of gravity < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Law of Universal Gravitation (Newton)-Solar System • The gravitational force of the sun affects the movement of all the planets. This force helps them stay in orbit around the sun. • So, the force of gravity has an important role in maintaining the shape of the solar system. < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Weight and Gravitational Force • weight = the gravitational force on an object • SI unit of force = newton (N). • Weight can change with the location of the object in the universe. • spring scale < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Mass and Gravitational Force • • • • Mass = the amount of matter in an object kilograms (kg) or grams (g) Mass does not change when gravitational force changes. balance scale < Back Next > Preview Main Chapter 13 Section 1 Gravity: A Force of Attraction Gravity and Static Objects • Gravity also acts on nonmoving, or static, objects. < Back Next > Preview Main Lab: Mass and Weight < Back Next > Preview Main End of Section 1 < Back Next > Preview Main Gravity and Motion (Ch. 13, Sect. 2) < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion What You Will Learn • acceleration due to gravity • air resistance • projectile motion: horizontal motion and vertical motion. < Back Next > Preview Main Why It Matters • Gravity affects the motion of everything that you drop or throw. < Back Next > Preview Main BrainPop: Acceleration < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Gravity and Falling Objects • Acceleration = change in velocity over time • Review: velocity = change in speed and/or direction weight = gravitational force (unbalanced) < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Gravity and Falling Objects • All objects fall to the ground at the same rate because the force of gravity is the same for all objects near Earth’s surface. • Acceleration = 9.8 m/s2 < Back Next > Preview Main Gravity and Falling Objects: Show these forces, using vectors, on graph paper. < Back Next > Preview Main Calculating the Change in Velocity • Formula: Δv = g x t • Δv = change in velocity • g = acceleration due to gravity (always 9.8 m/s) • t = time object falls (seconds) Change in Velocity: Δv = 9.8 m/s x total seconds < Back Next > Preview Main Change in Velocity: Math Practice formula: Δv = 9.8 m/s x total seconds Δv = Δv = < Back Next > Preview Main Video Clip: The Physics of Skydiving < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Air Resistance and Falling Objects • Air resistance is the force that opposes the motion of objects through air. • Air resistance slows the acceleration of falling objects. < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Air Resistance and Falling Objects • The amount of air resistance acting on a falling object depends on the size, shape, and speed of the object. < Back Next > Preview Main Chapter 13 Forces and Motion Show these forces, using vectors, on graph paper: < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Air Resistance and Falling Objects • An object falls at its terminal velocity when the upward force of air resistance equals the downward force of gravity. < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Air Resistance and Falling Objects • An object is in free fall if gravity is the only force acting on it. • It can only happen in a vacuum or outer space, where there’s no air. < Back Next > Preview Main Lab: Parachutes and Air Resistance < Back Next > Preview Main Projectile Motion and Gravity • vertical motion: gravity accelerates at 9.8 m/s2 (if air resistance is ignored). < Back Next > Preview Main Projectile Motion and Gravity • horizontal motion: not affected by gravity < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Projectile Motion and Gravity • horizontal movement + vertical movement = a curved path < Back Next > Preview Main Chapter 13 Forces and Motion Show these forces, using vectors, on graph paper: < Back Next > Preview Main Poster Project: Projectile Motion < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Orbiting and Gravity • An object is orbiting when it is moving around another object in space. < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion Orbiting and Gravity • The two movements that come together to form an orbit are similar to the horizontal and vertical movements in projectile motion. < Back Next > Preview Main BrainPop: Space Flight < Back Next > Preview Main Chapter 13 Forces and Motion Show these forces, using vectors, on graph paper: < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion • The path of an orbiting object is not quite a circle. Instead, the path is an ellipse. Orbiting and Gravity • Centripetal force is the unbalanced force that makes objects move in an elliptical path. • Gravity provides the centripetal force that keeps objects in orbit. < Back Next > Preview Main Lab: Circling Marbles < Back Next > Preview Main Chapter 13 Section 2 Gravity and Motion • Gravity helps maintain the shape of the solar system by keeping large objects such as the planets in their orbit around the sun. Orbiting and Gravity • Gravity also affects the movement of very small objects in the solar system, such as the tiny particles that make up the rings of Saturn. < Back Next > Preview Main End of Section 2 < Back Next > Preview Main Chapter 13 Section 3 Newton's Laws of Motion What You Will Learn Newton’s three laws of motion < Back Next > Preview Main Chapter 13 Section 3 Newton's Laws of Motion Newton’s First Law • An object at rest will remain at rest unless acted upon by an unbalanced force. • An object in motion will remain in motion at a constant speed and in a straight line unless acted upon by an unbalanced force. < Back Next > Preview Main Newton’s First Law • Friction makes Newton’s first law difficult • aka “law of inertia” • mass is a measure of inertia. – small mass = less inertia – large mass = more inertia < Back Next > Preview Main Chapter 13 Section 3 Newton's Laws of Motion Newton’s Second Law of Motion • Acceleration of an object depends on the mass and the amount of force. • greater mass = greater the force needed • greater force = increase in acceleration < Back Next > Preview Main Chapter 13 Forces and Motion < Back Next > Preview Main Chapter 13 Section 3 Newton's Laws of Motion Newton’s Third Law of Motion • All forces act in pairs. • When a force is exerted, there is always an equal and opposite reaction force. < Back Next > Preview Main Chapter 13 Section 3 Newton's Laws of Motion Newton’s First Law • PBS Teachers — Resources For The Classroom < Back Next > Preview Main End of Section 3 < Back Next > Preview Main