Paul Dundon’s Weblog


A little cheese and a little whine

Less spin, more swing

Not a post about the upcoming election, but another physics problem.

There’s an ad on TV at the moment where a couple hook their car up to a crane and accelerate underneath it so that, when the cables become taut, they are propelled into the air. Is this possible, we ask? The answer is: sort of – you just need a really high performance engine.

Full details (apologies for the PDF) are here. The solution rests on considering a situation in which the car is a frictionless pendulum (with a hole underneath the crane to allow it to swing) and then calculating the velocity of the car as it ascends past the level of the road. I assume that this is the velocity needed to achieve take-off in the actual scenario. I think this is valid but stand to be corrected.

Incidentally, before you go out and try this, I’m not convinced the cables would remain taut for the descent or what speed the car would hit the ground at.

Filed under: Maths

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My Bookshelf

The Golden Bough
The Value of Nothing
The Fire
A Wolf at the Table
Devil Bones

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