A full water bottle has a mass of 0.75 kg. Take g = 9.8 N/kg. Enter the bottle's weight in N.
Vada lifts a toolbox from the floor onto a shelf 1.5 m up. The toolbox weighs 20 N. Near the top it slips from her hands, drops, and lands hard enough to dent the floorboard.
The falling toolbox picked up speed and hit hard. Where did that energy come from?
Go back to the lift. To raise the toolbox at a steady speed, Vada's lifting force must match the toolbox's weight: 20 N, directed upward.
That force acts through the 1.5 m of height gained, so the lift does work against gravity: 20 × 1.5 = 30 J.
Those 30 J do not disappear. They are stored with the raised toolbox.
Let the toolbox go, and gravity hands the stored energy back: the toolbox speeds up as it falls. That is the energy that dented the floor.
A second lift: a 60 N backpack raised 2.0 m onto a locker shelf stores 60 × 2.0 = 120 J.
A third: an 8.0 N book raised 0.50 m onto a desk stores 8.0 × 0.50 = 4.0 J.
More weight stores more energy. More height gained stores more energy. The stored amount is always weight times height gained.
Wells raises a 35 N paint can from the floor to a 2.0 m shelf at a steady speed. Enter the energy the lift stores, in J.
A mover raises a 150 N box from the floor to a 1.2 m dolly platform at a steady speed. How much energy does the lift store?
Write down the values:
weight = 150 N, height gained = 1.2 m
Write down the relation:
stored energy = weight × height gained
Substitute in the values, and calculate:
stored energy = 150 × 1.2 = 180
The lift stores 180 J.
The same mover raises an identical 150 N box only 0.60 m, onto a low cart. How much energy does that lift store?
Write down the values:
weight = 150 N, height gained = 0.60 m
Write down the relation:
stored energy = weight × height gained
Substitute in the values, and calculate:
stored energy = 150 × 0.60 = 90
The lift stores 90 J: half the height gained, half the energy stored.
An elevator raises a 900 N crate through 4.0 m at a steady speed. Why does the ride up store energy with the crate?
Xenia raises the same 50 N crate twice: first from the floor onto a 1.0 m bench, then from the floor onto a 2.0 m shelf. How does the shelf lift's stored energy compare with the bench lift's?
Yael raises a 25 N flower pot from the patio to a window ledge 1.6 m up, at a steady speed. Enter the energy the lift stores, in J.
A stagehand slowly raises a 45 N sandbag through 3.0 m of height on a rope. The energy stored by the raising equals...
A stage crew hauls a 120 N light fixture from the stage floor up into the rigging, 3.5 m above, at a steady speed. Enter the energy the haul stores, in J.