Question

Why does the wall break the egg but the foam does not?

Answer

The layman’s answer would be “because the wall is very hard but the foam is very soft”.

The A-level answer would be “because the foam, being soft and yielding to the incoming egg, results in a longer impact duration Δt. Since force is equal to the rate of change of momentum, this results in a smaller impact force F= Δp/Δt (Newton’s 2^nd Law)

P.S. Note that the impulses exerted by both the wall and the foam are exactly the same, since the momentum change (Δp=0-p_i) is the same in both cases.

P.S. The force exerted by the foam is also spread out over a larger area. So this is another reason why the foam did not break the egg.

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