If no friction acts on a diver during a dive, then which of the following statements is true?
A.The total mechanical energy of the system increases.
B.Potential energy can be converted into kinetic energy but not vice versa
C.(KE+ PE)beginning = (KE + PE)end
D.all of the above
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Based on the given information, if no friction acts on a diver during a dive, then the only force acting on the diver is gravity. This means that the mechanical energy of the system is conserved.
Option A: The total mechanical energy of the system increases - This statement is not true because mechanical energy is conserved when no external forces, such as friction, are acting on the system.
Option B: Potential energy can be converted into kinetic energy but not vice versa - This statement is not true. In the absence of friction, potential energy can be converted into kinetic energy and vice versa because mechanical energy is conserved.
Option C: (KE + PE) beginning = (KE + PE) end - This statement is true. As mechanical energy is conserved when no external forces are acting, the sum of kinetic energy and potential energy at the beginning of the dive should be equal to the sum of kinetic energy and potential energy at the end of the dive.
Therefore, the correct answer is C. (KE + PE) beginning = (KE + PE) end.
Based on the information given, we are told that no friction acts on a diver during a dive.
A. The total mechanical energy of the system increases: This statement is not true because in the absence of friction, mechanical energy (the sum of kinetic energy and potential energy) is conserved. Friction is what typically causes energy loss in systems.
B. Potential energy can be converted into kinetic energy but not vice versa: This statement is not true. In the absence of friction, both potential energy and kinetic energy can freely interchange. As the diver falls, potential energy decreases and kinetic energy increases. And vice versa, as the diver moves upward, kinetic energy decreases and potential energy increases.
C. (KE + PE) beginning = (KE + PE) end: This statement is true. In the absence of friction, the total mechanical energy (the sum of kinetic and potential energy) remains constant throughout the dive. Therefore, the initial mechanical energy (KE + PE) at the beginning of the dive is equal to the final mechanical energy (KE + PE) at the end of the dive.
Therefore, the correct answer is C. (KE + PE) beginning = (KE + PE) end.