As a joke, Sam asks, "Which weighs more, a pound of feathers or a pound of lead?" Dave answers, "Lead, of course!" Why does Dave make this mistake even though he knows that both weigh the same? What concept is he thinking of?

Thank you for the opportunity to help you with your question!

Hi, thanks for your question.

This is a fairly common error. Weight can be defined as the product of mass (m) and the local gravitational acceleration (g). If the mass of two items is the same, and given the same g, their weight should be equal.

However, the confusion arises in such examples, because one tends to think of lead having more density than feathers and hence, the error. Therefore, one should not confuse weight with density (mass divided by volume).

I hope this helps.

Best wishes.

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