How much sand should Jones have used in Raiders of the Lost Ark?

In the movie Raiders Of the Lost Ark Jones replaces a golden statue with a bag of sand. I know that sand does not have the same density as gold, so a bag of sand the same size as the statue would not weigh the same. How could he have determined what the proper amount of sand it would have taken to equal the weight of the gold? He can't remove it, and their is no way to put it in water and figure the weight by water displacement. I am stumped as to how he could have been able to guess the amount of sand would have been required so it would have appeared that the Golden statue was still in place. Any help is appreciated. Anna

If he didn't know the volume of the statue in advance he'd have to guess. In the movie, he hesitates, removes some sand from the bag, and then swaps it with the statue. But he doesn't get it right, because the trap is sprung.

It looks to me like the sand bag is close in volume to the statue. As you've pointed out, the density of sand is quite different from the density of gold. Different kinds of sand have different densities, but 2.3 g/mL is a typical value. Gold has a density of 19.3 g/mL, so he needed a volume of sand that was (19.3 g/mL)/(2.3 g/mL) = 8.4 times the volume of the statue. Jones actually took sand away, when he should have added it.

The statue fit in one hand easily. I'd guess it was somewhere around 1 L in volume. That would put its weight at around 19 kg, or about 42 lbs. They were tossing it about as though it weighed much less than that when they were running through the tomb, so perhaps it was hollow, or just coated in gold.

(In our next episode, we consider the capacitance required for the Ark of the Covenant to produce a bolt of lightning capable of melting two dozen Nazis...)

Author: Fred Senese senese@antoine.frostburg.edu

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