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Q & A: energy to hold something up?

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Most recent answer: 03/06/2015
Q:
A helicopter hovering above a landing pad expends significant energy resisting gravity in order to hover. Once it lands and cuts its engines, the landing pad now bears the burden of resisting the force of gravity on the helicopter. Where does the landing pad get the energy to do so? Thanks.
- Michael Gardiner (age 47)
Chicago, IL
A:

This sounds strange at first, but it takes no energy flow to keep the helicopter up on the ground. It's not going anywhere, so the work done on it (force x distance) is zero.

So why does it take work to keep the helicopter up in the air? If it just hovers, no work is being done on it, for the same reason. The way that it's kept up, however, is by the blades pushing air down, and the air does move in response to the force from the blades. So they're doing work on the air. That means the engine must supply energy.

Mike W.

p.s. You might have a look at a related discussion: .


(published on 03/06/2015)

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