Why do bumper cars have rubber bumpers

the same reason why cars have rubber wheels;
because it is durable, semi shock absorbent, and most importantly very cheap to produce

Because of rubber's natural property of the reflection of kinetic energy in the form of recoil. With that, when two bumper cars collide, they really bump harder, otherwise they'd just smack into each other and sit there, crashed and broken.

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As a result of elastic's normal property of the impression of motor vitality as force. With that, when two amusement carts impact, they truly knock harder, else they'd simply smack into each other and stay there, smashed and broken.

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Because of Rubber Seals natural property of the reflection of kinetic energy in the form of recoil. If you are interested to get more detail about this topic then go through this website https://westernrubbers.com/product/rubber-seals/