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
I think it's C.
Yes, the answer is C, because KE + PE = A constant.
You are correct. The statement (C) is true in this scenario. In the absence of friction, the total mechanical energy of the diver, which includes both kinetic energy (KE) and potential energy (PE), remains constant throughout the dive. This means that the sum of the initial KE and PE is equal to the sum of the final KE and PE. Therefore, (KE + PE) beginning = (KE + PE) end.
To determine the correct statement, let's analyze each option:
A. The total mechanical energy of the system increases:
In the absence of friction, the mechanical energy of the system remains constant since no external work is done on or by the system. So, option A is not correct.
B. Potential energy can be converted into kinetic energy, but not vice versa:
In the absence of friction, the total mechanical energy remains constant (as discussed in option A). This means that potential energy can be converted into kinetic energy and vice versa throughout the dive, maintaining the total mechanical energy of the system. So, option B is not correct.
C. (KE + PE)beginning = (KE + PE)end:
This statement directly relates to the conservation of mechanical energy. Since there is no friction acting on the diver during the dive, the mechanical energy should indeed be conserved. This means that 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. Thus, option C is correct.
D. All of the above:
As discussed, options A and B are incorrect. However, option C is correct. Therefore, the correct answer is option C.
So, you were right. The correct statement is C.