A parcel is lifted a vertical distance, hhh, from the floor to a table.
The gravitational potential energy store of the parcel increases by 15 J.
The parcel is then lifted a further vertical distance, hhh, from the table onto a shelf.
What is the total increase in the gravitational potential energy store of the parcel when it is lifted from the floor to the shelf?
7.5 J7.5\text{ J}7.5 J
15 J15\text{ J}15 J
30 J30\text{ J}30 J
45 J45\text{ J}45 J