At the end of the original 1969 movie of The Italian Job, the thieves are in a bus hanging over the edge of a cliff, with a stack of gold bars about to slide out of the back doors. All the protagonists crowd to the front of the bus to balance out the weight of the gold. Their problem is they can’t get at the gold, because every time they try to edge down the bus to grab it, the bus tips again and the gold slides nearer the doors. The movie ends before the dilemma is resolved. Assuming no outside action is permissible, how could the thieves save the gold?
• Having so ingeniously stolen the gold in the first place, this final little problem would not have caused much consternation among the gang. They would strip out enough overhead internal wiring to fashion a stiff “rope”, lasso the pallet of gold and drag it to the front of the coach. Next, they would dismantle the pallet and use the main timbers to inch the coach back on to the road using a rowing motion.
Tony Holkham, Boncath, Pembrokeshire, UK
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• There are several ways to solve such a balance problem. If the thieves are armed they could shoot and puncture the bus’s fuel tank to drain it; the tank is typically in the rear of a bus and thus at the same end as the gold. Shooting the tank would not ignite the fuel, and draining it would tip the balance toward the thieves. Alternatively, a more time consuming approach would be to run the engine until the fuel runs out. Again this would tilt the balance toward the front of the bus.
“Shooting the fuel tank would not ignite it, and draining it would tip the coach towards the thieves”
Another approach would be to break the windscreen so the heaviest of the protagonists can crawl out of the bus and hang from the front bumper, increasing their distance from the fulcrum and perhaps creating enough leverage for the lightest of the gang to reach some bars. Once a few bars are transported to the front of the bus the balance would be shifted enough to move the rest of them.
One more idea is for the thieves to escape from the bus via the broken windscreen all at the same time. The bus would fall but they would all survive. A standard gold bar, which weighs about 12.4 kilograms, is not easily broken or washed away. If the gang hiked down the cliff the bars should be easy enough to find, even if they were not contained by the smashed bus. Presumably the thieves would know how many to search for.
Anthony Castaldo, San Antonio, Texas, US
• In 2008, to promote awareness of science, the UK’s Royal Society of Chemistry asked the same question, with the conditions that the solution took less than 30 minutes to complete and did not involve a helicopter.
The winning answer, by John Godwin of Surrey, UK, was for the gang to first break and remove two large side windows just aft of the pivot point and let the glass fall outside to lose its weight, followed by breaking two windows over the two front axles, keeping the broken glass on board to keep its weight for balance. One of the gang would then climb out through the front broken windows (but rest his weight on the ground) and deflate the bus’s front tyres, to reduce rocking movement about the pivot point. He would then drain the fuel tank, which was aft of the pivot point; this would change the balance enough to let another man get out and gather heavy rocks to load the front of the bus. Then they could unload the bus until a suitable vehicle passes, hijack it and carry the gold away.
However, using the amounts given in the movie, the gold’s weight would have been 3200 kilograms, almost the exact weight of the it was in. The structural changes at the rear that would be needed to support the three 670 kg Minis the coach originally carried, plus the 3200 kg of gold, luggage and fuel, would mean the weight aft of the fulcrum the bus was rocking on would exceed the total weight of the bus, sadly crashing both bus and question into the bottom of the valley.
Robin Hill, Crynant, South Glamorgan, UK
You can read the winning entry of the Royal Society of Chemistry’s competition here: prospect.rsc.org/blogs/rsc/in-pictures-italian-job-entries – Ed
• The simple answer is that they could not save the gold. This is because the situation depicted is absurd. When I taught physics I would use this scenario to illustrate the very high density of gold.
To begin with, the amount of gold depicted would far outweigh the men on the coach so that their edging back and forth in the bus would have had very little effect. A cube of pure gold just 16 centimetres on each side would weigh more than an average man.
Also, the weight of gold in the back would have catapulted the coach over the edge as soon as it went out of control. If it did teeter on the edge by some film-maker’s miracle, the weight of gold would create a lot of friction between the palette it was standing on and the coach floor preventing it from sliding unless the angle was catastrophically large.
Great film though.
Dave Oldham, Kingsley, Northamptonshire, UK