If an engine must do 500 joules of work to pull a 10 kg load up to a heaight of 4 meters, what is the efficiency of the engine?

 

I got 8%.

 

Am I correct?

Don´t think so. Perhaps it´s best if you show us how you calculated your result so maybe someone can point out where your error lies.

Work done: 10kg*9.8N/kg*4=appx 400J

 

efficience= work done/500 * 100

 

I don't know what I'm doing wrong.

400/500 * 100% = 80%, not 8%

OH! I knew my question looked weird! I completely forgot the 0 in 80%!

 

So, let me rephrase. Am I correct in my answer of 80%?

That look good, yes. The reason I asked you to show your calculation (apart from that it´s always a good idea to do so) was that I assumed you might have forgotten the factor 9.81 m/s².