Hot air balloons rise and submarines sink but why? Both depend on the principle of upthrust. An Indian textile millionaire reportedly broke the world record for the highest flight in a hot air balloon. The balloon soared to 21,000 metres. Balloonists need to know how to alter the weight of the balloon in order to rise or to fall. Submarines take on water in order to dive and expel it to rise to the surface.
They label an explanation of how submarines work. They draw force arrows on a diagram of a hot air balloon and calculate how many children might be lifted.
- That when an object is submerged in water, the water provides an upward force (upthrust) on it
- To represent the direction of forces by arrows
- That weight is a force and is measured in newtons
These resources were initially developed in partnership with the Centre for Science Education, Sheffield Hallam University.