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Published byEsther Dean Modified over 5 years ago

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CHAPTER 3

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Newton’s Second Law of Motion F = m × a Force = mass × acceleration The faster you run into a wall, the more force you exert on that wall Units are kg×m/s 2 Units are Newtons (N)

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F = m x a You run into the wall at 50 N of force. Your mass is 10 kilograms. Calculate your acceleration. Carmine has a mass of 100 g, and he is running toward you at 2 m/s 2. Calculate the force he will hit you with. (Tricky)

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Friction Friction is the force that opposes motion between two surfaces touching each other There are 3 types: 1. static = not moving 2. sliding = pushing a heavy box across the floor 3. rolling = your car spinning its wheels on the ice

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Air Resistance Air resistance affects anything moving in earth’s atmosphere The amount depends on the speed, size, and shape of the object Negating air resistance, which will fall faster: a feather or a bowling ball?

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Terminal Velocity The force of air resistance increases with speed Remember that the acceleration due to gravity is always 9.8 m/s 2 When the object is falling so fast that it cancels the force due to gravity, it is now at terminal velocity and is no longer accelerating This is the greatest falling velocity possible

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Law of Gravitation Any two masses exert a gravitational force on each other The size of this force depends on the mass and the distance between the objects Greater the mass, greater the force Closer together, greater the force

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Weight vs. Mass Weight = mass × acceleration due to gravity (9.8 m/s 2 ) Weight is in Newtons Weight is a force Mass is in kg Mass is the measure of amount of matter an object contains

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Calculating weight How much does a person with a mass of 70kg weigh on planet Earth? How much does a baby with a mass of 500g weigh on planet Earth? (Tricky)

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Projectile Motion When you throw a ball on Earth, there are two forces working on it Vertical force pulling down (gravity) Horizontal force pushing out (your throw)

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Newton’s Third Law of Motion For every action there is an equal and opposite reaction Ex: rocket propulsion

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Momentum momentum = mass × velocity p = m × v Law of Conservation of Momentum Momentum can be transferred from one object to another Total momentum of the system remains the same

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Calculating momentum Compare the momentums of a 50kg dolphin swimming 16.4m/s and a 6,300kg elephant walking 0.11m/s.

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