The energy changes from potential to kinetic. All of the energy is in the potential when the pendulum is at its highest point and not moving. The pendulum then starts to move and the energy is shifted into kinetic energy. The kinetic energy is greatest at the bottom of the swing and the amount of energy is equal to the maximum potential energy.
Lithium=li
Iron=Fe
Helium=He
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12 times breathe give 240 ml of pure 
. Each breathe gives 20 ml of .
Let us consider, volume of air per breathe= x ml.
Pure from inhaled air= 
ml and Pure from exhaled air= 
ml.
Pure from inhaled and exhaled air= 20 ml
So, + = 20
Therefore, x = 55.5 ml
So, volume of air per breath= 55.5 ml.
Gold is found in pure state in nature but not the iron because gold is un-reactive metal, so it does not react with other element in normal condition but iron is reactive metal so it reacts with atmospheric oxygen in presence of moist (water) to form oxide.
Explanation:
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All of the above. If you are going to narrow it down, it would be high voltage and radioactivity.
