A roofer rolls a magnetic sweeper across your lawn after you get a new roof. He needs to pick up the nails dropped during the job. How does the potential energy of the system change as picks up a nail?
The potential energy of the system increases as the nail is picked up, as the magnetic sweeper is doing work to move the nail from the ground to a higher elevation.
The potential energy of a system is the stored energy by virtue of an object's position relative to other objects. In this case, the potential energy of the roofer-nail system changes as the roofer picks up a nail.
Initially, when the roofer rolls the magnetic sweeper across your lawn, the nails are scattered on the ground, and they possess potential energy due to their position relative to the Earth's surface. This potential energy is determined by the nails' height above a reference level, such as the ground.
As the roofer picks up a nail using the magnetic sweeper, the nail's position changes from being on the ground to being attached to the sweeper or in the roofer's hand. Since the nail is now closer to the Earth's surface, its height above the reference level is reduced, resulting in a decrease in potential energy.
Therefore, as the roofer picks up a nail, the potential energy of the system decreases.
Potential energy is the energy an object or system possesses due to its position or configuration. In this case, the potential energy of the system refers to the change in potential energy of the roofer and the magnetic sweeper as the roofer picks up a nail.
Assuming there are no other external factors affecting the system, such as gravity or other forces, the potential energy of the system remains constant as the roofer rolls the magnetic sweeper without picking up a nail. However, when the roofer picks up a nail, the potential energy of the system decreases.
This decrease in potential energy occurs because the magnetic sweeper gains the energy associated with the magnetic attraction between the nail and the sweeper. As the nail is lifted away from the ground, the potential energy of the system is converted into the stored energy of the magnetic force between the nail and the sweeper.