Before the invention of electric fans, chimneys and fireplaces were used to ventilate homes and keep air moving.
The passage below explains the movement of air near a fireplace.
Choose the correct words from the box to complete the passage. Each word may be used once, more than once, or not at all:
conduction, contracts, faster, expands, increases, convection, decreases, slower
"Air is heated by the fire and the air molecules move __________ .
The air __________ as the molecules move further apart.
The density of the air __________ and the hot air rises.
Cold air flows in to replace the hot air and the process continues as a __________ current."
A cargo crate of mass 120 kg is lifted 15 m vertically upwards by a crane.
State the equation linking gravitational potential energy (GPE), mass, ggg, and height.
Calculate the gain in GPE when the crate is lifted 15 m.
State the work done in lifting the crate.