Final answer:
Out of the given options, a boy standing on top of a building has potential energy, whereas a descending airplane has both kinetic and potential energy. A book on a table and an apple on a tree have potential energy. To calculate potential energy, mass and height are needed, and mechanical energy combines both kinetic and potential energy.
Step-by-step explanation:
The question asks which options contain systems that possess both kinetic energy and potential energy. Kinetic energy is the energy of motion, while potential energy is stored energy due to an object's position, composition, or condition. The options given are:
- A boy standing on top of a building - has potential energy due to his height above the ground.
- A descending airplane moving with velocity v - has kinetic energy due to its motion and potential energy due to its height above the ground.
- A book placed on a table - has potential energy due to its position above the ground but no kinetic energy as it is not moving.
- An apple on a tree - has potential energy due to its position above the ground but no kinetic energy as it is not moving.
To calculate the potential energy of an object like the apple, we need to know the mass of the object and the height from the reference point. Mechanical energy is the sum of kinetic and potential energies; however, it is not necessarily at a maximum at the beginning of the motion unless the system is designed for that condition, such as a roller coaster at the top of a track.