energy, work, and power
DESCRIPTION
Energy, Work, and Power. Some Definitions. Work= Force X Distance. If a person exerts 20 Newtons of force to move 5 meters, he has done 100 Joules of work. W= 20N X 5m = 100 J. Solve this Problem: A ball weighing three Newtons falls a distance of 4 meters. What work has been done?. - PowerPoint PPT PresentationTRANSCRIPT
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Energy, Work, and Power
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Some Definitions
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Work= Force X Distance
If a person exerts 20 Newtons of force to move 5 meters, he has done 100 Joules of work.
W= 20N X 5m = 100 J
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Solve this Problem:
A ball weighing three Newtons falls a distance of 4 meters. What work has been done?
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Work Done?
a. A teacher applies a force to a wall and becomes exhausted. Explanation:________________________________________________________________________
Yes or No
b. A weightlifter lifts a barbell over her head. Explanation:________________________________________________________________________
Yes or No
c. A waiter carries a tray full of meals across the dining room at a constant speed. Explanation:________________________________________________________________________
Yes or No
d. A rolling marble down hits a note card and moves it across a table. Explanation:________________________________________________________________________
Yes of No
e. A shot-putter launches the shot. Explanation:________________________________________________________________________
Yes or No
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Let's Practice!
Tap the ball to reveal the assignment
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Mechanical Advantage and Mechanical Efficiency
Both ratios (fractions and percentages) show us how well the machine works.
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Mechanical Efficiency--How well the machine uses the energy you put into it. It compares the work you do to the machine and the work you get out. The work you get out of the machine is always less than the work you put in and you lose some energy to friction.
ME= work outputwork input
X 100
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Mechanical Advantage--How much force you get out of the machine. Your mechanical advantage should be greater than 1 for the machine to be useful.
MA = Force outputForce input
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Attachments
Practice Problems on Work.docx