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Answers for Practice Questions
1.
Wo= 400N X 2m
Wo= 800 J

Wi= 300N X 5m
Wi= 1500 J

ME= Wo/Wi X 100%
ME= 800/1500 X 100%
ME= 53%

Energy wasted as friction = 100% - ME
= 100% - 53%
= 47%

2.
Wo= 800N X 3m
Wo= 2400 J

Wi= 450 X 7m
Wi= 3150 J

ME= Wo/Wi X 100%
ME= 2400/3150 X 100%
ME= 76%

Energy wasted as friction = 100% - ME
= 100% - 76%
= 24%

3. You can improve efficiency or lower friction by adding wheels or using lubricants.

4. A lubricant is a solid or liquid such as greases and oils that reduce the friction on a machine by smoothing the surface.

5. No it is impossible because the machine always gives off heat energy.