A car is a vehicle or a locomotive generally used for transportation of people(and other living things viz. animals, plants, etc.) or things(non living things such as tables, computers, grains, cement, etc.).
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Every car is used primarily on transportation, either human person, animal, etc.
Because of your poo and pee
It is useful to cars because it helps them move for one place to another
Fuels are useful to us. It is useful to us because we use it for our cars
Cars tomove
Toy cars are so useful because they can keep children occupyed (they are good fun) and also they can be collected and can be sold for even more.
Cars are useful as they take us from our homes to our jobs, to the store, to events we attend. In western society the car has become a necessity.
stopping cars Friction is useful to start a fire with sticks.
you can get to places faster
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chemical potential energy
harmful
Transportation of passengers and cargo.
Many things are not necessary. Some of them, like fast cars, serve useful purposes.