Final answer:
The correct activity that involves force without changing energy is carrying an object without acceleration at the same height, as no work is done. To carry books without doing work, the books must be moved without acceleration and while keeping their height constant.
Step-by-step explanation:
The question relates to the concept of work and energy in the context of physics. When considering which activity requires a person to exert force on an object that causes the object to move but does not change the kinetic or potential energy of the object, the key is to identify an activity where the movement does not involve a change in the object's position in a way that would alter its energy.
Therefore, among the given options, the correct answer is d. Carrying an object without acceleration at the same height because this involves moving an object with constant velocity at a constant height, which implies that there is no net work done on the object as its energy does not change.
On the other hand, in order to carry books to school without changing the kinetic or potential energy of the books or doing any work, the correct statement is a. By moving the book without acceleration and keeping the height of the book constant.
This describes a situation where the books are carried horizontally at a steady pace without gaining or losing height, thus ensuring that their energy remains unchanged and no work is done on the books according to the physical definition of work.