<span>D. The screw changes the direction of a force - it converts linear force into rotational force. It also reduces the force required - the closer the threads, the smaller the input force required to get the same output force.</span>
This is a tricky question. All that matters are ratios of percentages, not percentages themselves. So no one should directly compare 27.2 with 42.9. We must and shall compare the ratios (27.2 to 72.8) and (42.9 to 57.1).
Take them both down to 1 to and see what happens.
Working out the formulas knowing atomic masses is a bit beside the point; this is how people first DISCOVERED the idea of atomic mass.
A
Carbon Oxygen
27.2g 72.8g (100-27.2)
Moles 27.2/12 72.8/16
2.27 4.55
Ratio 1 2
Do the same with the other
Hmm.... Oxygen support combustion. Other than that, rusting occur when oxygen is combined with metal. When iron rusts, it combines with oxygen. Hope it helps.
