A student lifts a box from the floor onto a shelf.
The Figure shows the box on the floor and on the shelf.
Figure
[Image brief: A simple side-view line drawing on a white background. A horizontal floor line runs across the bottom of the image, labelled "floor". On the right, a wall-mounted shelf is drawn as a thick horizontal plank fixed to a vertical wall line. A closed cardboard box (a cuboid with a strip of tape across the top) sits on the shelf, drawn with solid black lines and labelled "box on shelf". Directly below the shelf, an identical box is drawn on the floor with dashed outlines, labelled "box on floor". A vertical double-headed arrow runs from the floor line to the top surface of the shelf, labelled "1.6 m". A simple figure of a student stands on the left, facing the shelf, with arms by the sides. No other numbers or labels. Sans-serif font, black on white.]
The mass of the box is 3.5 kg.
Gravitational field strength (ggg) = 10 N/kg
Write down the equation linking change in gravitational potential energy, mass, gravitational field strength and change in vertical height.
Calculate the change in gravitational potential energy of the box when it is lifted onto the shelf.
The student lifts a second box from the floor onto the same shelf.
The gravitational potential energy of the second box increases by 72 J.
Calculate the mass of the second box.
The student says:
'The box would gain more gravitational potential energy if I carried it up a long ramp to the shelf instead of lifting it straight up.'
Explain whether the student is correct.