Physics Machine efficiency question.
HOME > Physics > Physics Machine efficiency question.

# Physics Machine efficiency question.

[From: ] [author: ] [Date: 11-06-19] [Hit: ]
mass a distance of 5.65 meters using a machine 72.5 percent efficient?If the answer is 16420.07 N, Im right!......
Hi, I want to make sure I understand the concept of efficiency if you guys get the same answer as me.

What work is required to lift a 215 kg. mass a distance of 5.65 meters using a machine 72.5 percent efficient?

If the answer is 16420.07 N, I'm right! If it's not, and it probably will be wrong, can you please show me your work?

-
W = m*g*D/η = 215*9.8*5.65/.725 = 16420.07 J (not Newtons, a measure of force)

Keep up the good work!

-
The work done in lifting the object is equal to it's change in gravitational potentional energy. However since the machine is only 72.5% efficient this means that only 72.5% of the work it does goes into changing the gravitational potential energy of the mass.

Therefore:

72.5/100 * Work done by machine = m*g*h
= 215*9.8*5.65
= 11,904.55 J
Therefore:
Work done by machine = 11,904.55/(72.5/100)
= 16,420.07 J (!!!)

Your working is correct and you have the correct answer as far as the number is concerned. However, the unit is Joules (J) not N (newtons). Work required to lift is the energy given to the mass when it is lifted not the force applied to the mass as it is lifted.
1
keywords: efficiency,Machine,question,Physics,Physics Machine efficiency question.
New
Hot
© 2008-2010 http://www.science-mathematics.com . Program by zplan cms. Theme by wukong .