Money speeds up Big Ben

'If an old English penny is added to the pendulum it gains two fifths of a second a day. We have yet to work out what a euro will do' Thwaites and Reed, Big Ben maintenance

Apparently, Big Ben is being cleaned-up, or so we learn at: http://news.bbc.co.uk/low/english/uk/newsid_1501000/ 1501943.stm

Any takers on the time-shortening powers of a Euro? (or is it a euro?)

regards, ct

An old penny weighed exactly a third of an avoirdupois ounce. I think a new penny is an eighth of an ounce, but it's a long time since I traded any hashish.

I don't know what a euro will weigh.

)>'If an old English penny is added to the pendulum it gains two fifths )>of a second a day. We have yet to work out what a euro will do' )>Thwaites and Reed, Big Ben maintenance

Doesn't that depend on _where_ the penny is added ? After all, the _only_ thing that determines the period of an (ideal) pendulum is the distance from the point of gravity to the point of rotation, isn't it ?

Although maybe the penny induces some extra air resistance, or some resistance in the bearings, because of the added weight. Naah, that would make it lose 2/5 of a second, instead of gaining it.

There's really only one place that you'd consider adding a penny to the pendulum of the clock associated with Big Ben. The weight at the bottom of the pendulum has a flat top, and they just drop the pennies onto it. Anywhere else and you'd have to stop the clock and use some sort of attachment device.

)>>'If an old English penny is added to the pendulum it gains two fifths )>>of a second a day. We have yet to work out what a euro will do' )>>Thwaites and Reed, Big Ben maintenance )> )>Doesn't that depend on _where_ the penny is added ? ) ) There's really only one place that you'd consider adding a penny to the ) pendulum of the clock associated with Big Ben. The weight at the bottom ) of the pendulum has a flat top, and they just drop the pennies onto it. ) Anywhere else and you'd have to stop the clock and use some sort of ) attachment device.

Yeah, I had a hunch, but I thought that would be more appropriate in the Notre Dame, instead of the Big Ben.

To make a clock run ahead by adding pennies, you'd have to add the pennies above the center of gravity. On top of the weight would be the logical choice.

So, now that we know the position is fixed, can we derive a ratio between gained time per day and weight of added coin ? Or do we need extra information ? (swinging frequency of the pendulum wouldn't hurt, I guess)

According to http://www.24carat.co.uk/eurocoins.html, a 1 Euro coin has a mass of 7.5 grams. Since the coin is small compared to the pendulum, a linear approximation should be quite accurate, as long as the period is a differentiable function of the added mass. Thus the Euro should add approximately 2/5 * 7.5/(1/3*28.35) = .3175 seconds per day.

Department of Mathematics http://www.math.ubc.ca/~israel University of British Columbia Vancouver, BC, Canada V6T 1Z2