When you rub your hands together on a cold day, you use friction to convert a. mechanical energy into thermal energy. b. thermal energy into nuclear energy. c. nuclear energy into electrical energy. d. electrical energy into electromagnetic energy.

the answer is a) mechanical energy into thermal energy.

a. mechanical energy into thermal energy.

Explanation:

The energy conversion actually start in chemical potential energy in food that is eaten and taken up by muscles. Muscles then take the broken down and digested food and use it to make energy which is mechanical energy as the muscle contracts and relaxes to rub hands together and this produces heat.

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.

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