If you throw 1 kg cotton and 1 kg watermelon at somone, why does the watermelon hit you harder despite it being the same weight?

Question

If you throw 1 kg cotton and 1 kg watermelon at somone, why does the watermelon hit you harder despite it being the same weight?

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Answer 1

Not a scientist involved in kinetic energy etc but here’s my take.

Assuming it’s thrown at the same speed it’s because of the density. A kilo of watermelon takes up one tenth of the volume of cotton wool. When it hits you, all the energy of the watermelon is transferred to your body (more or less) in one go. The cotton strikes you but it also has to squash (because it’s fluffy) so it takes longer to transfer the energy.

If you compress the cotton wool into a small block, it would hurt like hell.