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
In which of the following does Einstein’s famous equation apply?
A) driver bringing a car to a halt
B) collisions between objects
C) water falling in a waterfall
D) nuclear fission and fusion reactions
Thank you for your help! ^_^
D,D,D
For the first question, if no friction acts on a diver during a dive, then the only external force acting on the diver is gravity. Since no friction is present, there is no loss of mechanical energy due to work done against friction. This means that the total mechanical energy of the system (diver) is conserved.
From the given options, statement C) (KE + PE)beginning = (KE + PE)end is the correct answer. The sum of the kinetic energy (KE) and potential energy (PE) at the beginning is equal to the sum of the kinetic energy and potential energy at the end of the dive.
To understand why this answer is correct, we can look at the principle of conservation of mechanical energy. In the absence of external forces like friction, the total mechanical energy of a system remains constant. Mechanical energy is the sum of kinetic energy (energy due to motion) and potential energy (energy due to position or height). As the diver falls, potential energy decreases while kinetic energy increases, but the sum of both remains constant throughout the motion. Therefore, (KE + PE)beginning = (KE + PE)end.
Now, for the second question, Einstein's famous equation, E=mc², applies to option D) nuclear fission and fusion reactions. This equation relates energy (E), mass (m), and the speed of light (c). It states that energy is equal to mass times the speed of light squared.
In nuclear fission and fusion reactions, small amounts of mass are converted into large amounts of energy according to Einstein's equation. The equation highlights the equivalence between mass and energy, indicating that a small amount of mass can release a tremendous amount of energy. This plays a crucial role in understanding and calculating the energy released in nuclear reactions.
To summarize, the correct answers are:
1) C) (KE + PE)beginning = (KE + PE)end
2) D) nuclear fission and fusion reactions