55. A machine makes work easier by multiplying force or ____________________, or by changing direction. 56. Both the respiratory system and the circulatory system rely on the __________________ system, which automatically produces movement in the heart and the lungs.
55. A machine makes work easier by multiplying force or ____________________, or by changing direction. 56. Both the respiratory system and the circulatory system rely on the __________________ system, which automatically produces movement in the heart and the lungs.
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