Download - Forces in Motion
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Forces in Motion
What Do You Think?
How does the force of gravity affect falling
objects?
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Forces in Motion
Gravity causes all objects to fall toward the ground with the same acceleration, 9.8 m/s2.
http://mired.org/home/mwm/parachuting/floating2.jpeg
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Forces in Motion
A little vocabulary before we start…
• Force- a push or a pull• Velocity- the speed of an object
and its direction of motion.• Acceleration- the rate at which
the velocity changes.
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Forces in Motion
Activity
Drop a tennis ball and a golf ball from a table at the same height at the same time.
Which hits the ground first?
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Forces in Motion
• In the late 1500s, Galileo found that mass does not affect the time the object takes to fall to the ground.
• Both the elephant and the feather hit the ground at the same time.
• This only happens if there is NO air resistance.
http://www.physicsclassroom.com/mmedia/newtlaws/efff.html
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Forces in Motion
Air resistance is a fluid friction that opposes the motion of object through the air.
It slows down acceleration.
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Forces in Motion
Drop 2 sheets of paper- one crumpled in a tight ball and the other kept flat.
What happens? Why?
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Forces in Motion
Air resistance is affected by:
• The Size of the object
• The Shape of the object
• The Velocity of the object
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Forces in Motion
This is what happens to the elephant and feather when air resistance is present.
http://www.physicsclassroom.com/mmedia/newtlaws/efarm.htl
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Forces in Motion
An object is in free fall only if gravity is pulling it down and no other forces are acting on it.
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Forces in Motion
• Because air resistance is a force, free fall can only occur where there is no air, such as a vacuum (a place in which there is no matter) or in space.
• If the feather and the elephant were in free fall, they would hit the ground at the same time.
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Forces in Motion
• Astronauts appear to be “weightless” in space because of free fall.
• Both the astronaut and the space shuttle are falling toward the earth at the same rate.
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Forces in Motion
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How an orbit is formed
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Forces in Motion
Projectile Motion is the curved path an object follows when it is thrown or propelled near the surface of the Earth.
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Forces in Motion
Projectile motion has 2 components: horizontal and vertical.- When throwing a ball, horizontal motion occurs when the ball leaves your hand.- After the ball leaves your hand, gravity pulls it down giving it vertical motion.
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Forces in MotionProjectile Motion from a Baseball
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