You do 25 J of work to move a 4 N object 5 meters. What is your efficiency?

1 Answer
Jun 20, 2018

0.8 or 80%


Here, the total amount of energy provided by your body is 25 J. However the amount of energy required to move the object (useful energy) through 5 metres is 20 J. The other 5 J will be wasted and converted to other forms like heat in our muscles.

How did I get 20 J?

It's known that:

Work done = Energy transferred

Here, the work done is the product of force and displacement:

#W= f.s#


W= 4 x 5 = 20 J

Now what's the efficiency?

Here it is:

Useful output energy/ Total input energy


#20/25# = 0.8


#20/25# x 100= 80%