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Physical Science 1011. Chapter 2 Newton’s Laws of Motion. 2.1 Newton’s First Law of Motion. Every object continues in a state of rest, or in a state of motion in a straight line, at contanst speed, unless it is compelled to change that state by forces exerted upon it.
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Physical Science1011 Chapter 2 Newton’s Laws of Motion
2.1 Newton’s First Law of Motion • Every object continues in a state of rest, or in a state of motion in a straight line, at contanst speed, unless it is compelled to change that state by forces exerted upon it. • Usually called the Law of Inertia • Essentially the same as Galileo’s idea
2.2 Newton’s Second Law of Motion • The acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object. Net Force Acceleration = Mass
2.2 Newton’s Second Law of MotionAcceleration Due to Gravity • An object in free fall accelerates toward the Earth at 10 m/s2(if we neglect air resistance). • We assign the letter g to acceleration due to gravity. W g = W = mg m
2.2 Newton’s Second Law of MotionAcceleration Due to Gravity • Objects of differing masses will accelerate toward the Earth at the same rate (if air resistance is neglected). • This has been proven during an Apollo Mission to the Moon. A hammer and a feather were released at the same time. Both struck the ground at the same time.
2.2 Newton’s Second Law of MotionAcceleration Due to Gravity • A skydiver accelerates toward the ground. • As he does, air resistance increases to the point where it equals his weight. • The skydiver then stops accelerating and falls at a constant rate called Terminal Velocity of approximately 200 km/h (125 mi/h).
2.2 Newton’s Second Law of MotionAcceleration Due to Gravity • By opening his parachute, the skydiver increases the total force of air resistance, slowing him down to a speed that allows him to land without injury. (22 km/h or 14 mi/h)
2.3 Forces and Interactions • When you push on a wall, the wall pushes back.
2.4 Newton’s Third Law of Motion • Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. • For every action, there is an equal and opposite reaction.
2.5 Vectors and Scalars • Scalars have size • Mass, speed, volume, temperature • Vectors have size and direction • Velocity, acceleration, force
