# 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%

#### Explanation:

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:

So:

W= 4 x 5 = 20 J

**Now what's the efficiency?**

Here it is:

**Useful output energy/ Total input energy**

So:

Or: