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Chapter 12
Work, Power, & Machines
I. What is work?
A. Work – when force causes a change in an objects position.
1. Change must be in the direction force is applied.
Does this guy do work?
Yes b/c the car changed position
II. Measuring WorkA. The unit for work is the Joule (J).
A Joule is equal to lifting an apple 1 meter (about 3 feet off the ground.
An apple weighs about 4 ounces
Work = Force x Distance
Joules (J) = Newtons (N) x Meters (m)
Problem:An apple weighing 1 Newton falls a distance of 1 meter. How much work is done by the force of gravity?
GIVEN:F = 1 Nd = 1 mW = ?
WORK:W = F x dW = (1 N)(1 m)W = 1 J
F
W
d
Problem:While rowing in a race, John uses his arms to exert a force of 165 N per stroke while pulling the oar 0.8 m. How much work does he do in one stroke?
GIVEN:F = 165 Nd = 0.8 mW = ?
WORK:W = F x dW = (165 N)(0.8 m)W = 132 J
F
W
d
Assignment:
Make your paper look like this:
Work, Power, & MachinesABCDEFGH
Z
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