unit 15 lesson 4 what are newton’s laws? · 15/01/2019 · unit 15 lesson 4 what are newton’s...
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Unit 15 Lesson 4 What Are Newton’s Laws?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s First Law of Motion
Copyright © Houghton Mifflin Harcourt Publishing Company
• In the 1600s, Isaac Newton published a book about how objects move in the physical world.
• Newton summed up his ideas in three rules, or laws.
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s First Law of Motion
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• Newton’s first law describes inertia, or the tendency of objects to resist a change in motion.
• For example, when a car makes a sudden turn, your body pulls to the other side of the car.
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s First Law of Motion
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• Newton’s first law of motion states that no acceleration, or change in motion, can happen without an unbalanced force, or push or pull.
• In other words, objects at rest don’t move unless an unbalanced force acts on them.
• Objects in motion don’t slow down, speed up, stop, or turn unless a force makes them do so.
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s First Law of Motion
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Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Second Law of Motion
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• Newton’s second law of motion states that an object’s acceleration depends on two factors: the amount of force applied to the object and its mass.
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Second Law of Motion
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• The mass of an object affects how, or if, the object moves when a force is applied to it.
• Newton’s second law explains why you must use more force to move an object with a greater mass.
• This law can be written as an equation:
Force = mass x acceleration
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Second Law of Motion
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Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Second Law of Motion
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Third Law of Motion
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• Newton’s third law of motion states that whenever one object applies force to another, the second object applies an equal, opposite force to the first object.
• In other words, this law says that forces always act in pairs.
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Third Law of Motion
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• Sometimes scientists use the terms action force and reaction force to refer to a pair of forces.
• In other words, the two forces described above are equal in size and opposite in direction.
• For example, when leaning against a wall, your body applies force to the wall. The wall doesn’t move because it applies the same amount of force to you.
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Third Law of Motion
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Newton’s Third Law of Motion
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Motion in Space
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• Astronauts in orbit appear to be weightless.
• To understand motion of objects in space, it’s important to remember the difference between weight and mass.
• Mass refers to how much matter is in an object. Weight refers to how much force is applied to an object by gravity.
Unit 15 Lesson 4 What Are Newton’s Laws?
Motion in Space
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• Newton’s laws of motion apply to objects in space, because the laws involve mass, not weight.
• The mass of an object is the same on Earth and in space.
• An object’s weight can change because weight is related to the force of gravity at a particular location.
Unit 15 Lesson 4 What Are Newton’s Laws?
Motion in Space
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• Astronauts feel and look weightless because of microgravity.
• Microgravity occurs because Earth’s gravity causes the space station to fall toward Earth at a constant rate. Everything inside the space station falls at the same rate.
Unit 15 Lesson 4 What Are Newton’s Laws?
Motion in Space
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Unit 15 Lesson 4 What Are Newton’s Laws?
Motion in Space
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• Because astronauts are also in free fall, they appear to float.
Unit 15 Lesson 4 What Are Newton’s Laws?
Motion in Space
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 15 Lesson 4 What Are Newton’s Laws?
Copyright © Houghton Mifflin Harcourt Publishing Company