What is the efficiency of a block and tackle if you pull 25 m of rope with a force of 820 N to raise a 75 kg grandfather clock 15 m?

It's because 3 if it was 10 it wouldn't look right do it goes up to 4d

The chemical reactions lab we did is typically called a "copper plating lab,  because the acid solution cleaned the pennies and made the copper look shinier;   the acid solution cleaned the paperclips and made them look like pennies;   &   the copper from the pennies was removed, and then added to the paperclips. 

In atoms, the electron carries a negative elementary or unit charge; the proton carries a positive charge. the two types of charge are equal and opposite. in an atom of matter, an electrical charge occurs whenever the number of protons in the nucleus differs from the number of electrons surrounding that nucleus.