What exactly is work? My book confuses me:
a force can lift an object to a height h, or it can accelerate an object through gravity. In all these cases, a force displaces an object and change the object's total energy.
The examples it gives confuse me. On one hand, there is lifting and on, accelerating through gravity.
I can imagine how lifting will change total energy (kinetic + potential). It essentially gives it more potential energy, and does not take from it any kinetic energy. But just dropping an object and let gravity do the work does not seem to me to increase total energy. Because the total amounts of kinetic and potential energy should be equal. If just let drop, the object will gain kinetic and lose some potential. Not really anything added to the total energy.