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Motion and Force <ul><li>Chapter Twelve: Distance, Time, and Speed </li></ul><ul><li>Chapter Thirteen: Forces </li></ul><ul><li>Chapter Fourteen: Force and Motion </li></ul>
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Chapter Fourteen: Force and Motion <ul><li>14.1 Newton’s First and Third Laws </li></ul><ul><li>14.2 Newton’s Second Law </li></ul>
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Investigation 14B <ul><li>What is the relationship between force and motion? </li></ul>Newton’s Second Law
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14.2 Newton’s Second Law <ul><li>Acceleration is the rate at which your velocity (speed with direction) changes. </li></ul>
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14.2 Acceleration <ul><li>A car can change its velocity by speeding up, slowing down, or turning. </li></ul><ul><li>If an object’s acceleration is zero , the object could be moving at a constant speed in a straight line or could be stopped. </li></ul>
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<ul><li>To calculate acceleration, you divide the change in speed by the amount of time it takes for the change to happen. </li></ul>
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14.2 Acceleration <ul><li>If an object speeds up, it has a positive acceleration. </li></ul><ul><li>If it slows down, it has a negative acceleration. </li></ul>What is the acceleration of the sailboat?
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14.2 Force, mass and acceleration <ul><li>Force causes acceleration, and mass resists acceleration. </li></ul><ul><li>Newton’s second law relates the force on an object, the mass of the object, and its acceleration. </li></ul><ul><li>Force causes acceleration, and mass resists acceleration. </li></ul>
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<ul><li>The stronger the force on an object, the greater its acceleration. </li></ul><ul><ul><li>Force is directly proportional to acceleration. </li></ul></ul><ul><ul><li>If twice the force is applied, the acceleration is twice as great. </li></ul></ul>
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<ul><li>The greater the mass, the smaller the acceleration for a given force. </li></ul><ul><ul><li>Mass is inversely related to force. </li></ul></ul><ul><ul><li>An object with twice the mass will have half the acceleration if the same force is applied. </li></ul></ul>
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14.2 Applying the second law <ul><li>Keep the following important ideas in mind: </li></ul><ul><ul><li>1. The net force is what causes acceleration. </li></ul></ul><ul><ul><li>2. If there is no acceleration, the net force must be zero. </li></ul></ul><ul><ul><li>3. If there is acceleration, there must also be a net force. </li></ul></ul><ul><ul><li>4. The force unit of newtons is based on kilograms, meters, and seconds </li></ul></ul>
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14.2 Newton’s second law and gravity <ul><li>Gravitational force exists between all objects that have mass. </li></ul><ul><li>An object is in free fall if it is accelerating due to the force of gravity and no other forces are acting on it. </li></ul><ul><li>Objects in free fall on Earth accelerate downward at 9.8 m/s2, the acceleration due to gravity . </li></ul>
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14.2 Newton’s second law and gravity <ul><li>An object is in free fall if it is accelerating due to the force of gravity and no other forces are acting on it. </li></ul><ul><li>Objects in free fall on Earth accelerate downward at 9.8 m/s2, the acceleration due to gravity . </li></ul>
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14.2 Universal gravitation <ul><li>Gravitational force exists between all objects that have mass. </li></ul><ul><li>You do not notice gravity between ordinary objects because it takes a huge amount of mass to create enough force to notice. </li></ul>
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14.2 Universal gravitation <ul><li>The force of gravity between you and Earth is strong because the planet’s mass is huge. </li></ul><ul><li>Newton’s law of universal gravitation says the strength of the force depends on the mass of the objects and the distance between them. </li></ul>
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14.2 Orbital motion <ul><li>Newton’s second law can be used to explain the motion of planets, moons, and satellites in orbit. </li></ul><ul><li>The orbiting moon falls around Earth. </li></ul>Can you kick a soccer ball into orbit? Can we launch a soccer ball into orbit?
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Activity <ul><li>Newton’s three laws can be used to explain the motion of everyday objects. </li></ul><ul><li>In this activity you will build a car and apply Newton’s laws to explain how it works and why it moves as it does. </li></ul>Making a Spool Car
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