On 18 August 2019, an Australian living in Singapore threw a wine bottle from the seventh floor of a condominium. The bottle hit an elderly man, then bounced off and hit his wife.

The wife was injured. The man died. The Australian was sentenced to 1 year in jail.

The higher up you drop an object, the harder it hits the ground. We know that it falls because of the force of gravity, but why does it fall faster and faster?

What does a force do to an object?

Weight is a force. A force would actually cause an object to accelerate. This effect is described by Newton’s second law. When an object is dropped, it falls faster and faster. The speed increases by about 10 metres per second - every second.

So after 1 second, the speed is 10 m/s. After 2 s, it is 20 m/s After 3 s, it is 30 m/s, and so on.

If we estimate that one floor is about 3 m high, then the 7th floor is at about 21 m. Using a formula from school physics, we can calculate that the wine bottle would reach the ground floor with a speed of about 74 km/h, or 74 kilometres per hour.

This is as fast as a car going at high speed on the road. With a wine bottle at that speed, there is little chance of surviving a direct hit. This is why throwing things from high floors – or high-rise littering as it is called – is so dangerous.

Many people do not know this, because they are only familiar with what they have seen – like dropping a bottle on the floor. Or they do not care - blinded by emotion. It could be because they are angry or drunk - or both, as in the case of the Australian.

It could be for fun when a boy in Singapore threw a cat down from the 22nd floor in 2022. The boy might have seen cartoons like Bugs Bunny showing animals walking without a scratch after falling off high cliffs, and thought that it is the same in real life.

It is sad that a lack of basic knowledge can lead to unnecessary tragedy. Clearly, from the above accounts, this can be a problem for both child and adult. A proper understanding of physics can help prevent such tragedies.

Unfortunately, there remains a difficult problem in practice. A series of 2021 inspections by the Ministry of National Development shows that there are still dangerously placed items like flower pots that may fall off.

Apart from sending people around to talk to residents, the Sengkang Town Council for example imposed fines of $200 for first offence of letting something fall off from their flat, $500 for second and subsequent offence. (Not sure why the fine does not go up.)

The National Environmental Agency website stated in 2023 that if it is proved that littering act from a flat is committed, the owners or tenants will be presumed to have committed the act – meaning that they are guilty until proven innocent. What if some stranger had stolen the key and went into the flat ...

For now, the more cameras are placed around littering hot spots. As good citizens, we should do our civic duty and keep our own high floor flats free of the risk of falling objects.

And it always helps to learn more physics. A good understanding of physics can help save lives.

You can learn these concepts and more at Dr Hock's maths and physics tuition.