6.1. Work http://www.ck12.org
FIGURE 6.4
No work is done upon the object when
acts perpendicular to the displacement of
the object.FIGURE 6.5
A N*m is the same askg·m
2
s^2 which is given the name “Joule,” abbreviated “J.”
Therefore, the man inFigure6.5 has done 1500 J of work on the crate.
The Joule takes its name from the 19th-century British physicist James Prescott Joule (1818-1889), which we will
have more to say about in Chapter 14 (Thermodynamics).
Illustrative Example 6.1.3
The weightlifter inFigure6.6 is about to lift a barbell of mass 120 kg through a height of 0.85 m. How much work
will he do on the barbell?
Answer:W=F x= (mg)x= ( 120 )( 9. 8 )( 0. 85 ) = 999. 6 = 1000 J
Illustrative Example 6.1.4
The man inFigure6.7 is exerting a force of 300 N at angle of 25 degrees to the floor in order to pull the tire a
distance of 3.25 m. How much work is he doing on the tire?
Answer:Let’s sketchFigure6.7 in order to analyze the problem.