On Mon, Sep 09, 2002 at 12:43:40PM +1000, Terry Pacey wrote:
> Just a short time ago, I was watching Rainbow Lorikeets feeding in a tall
> Silky Oak (grevillia robusta) behind our place. Suddenly, one of the birds
> flapped its wings and took off vertically and with another flap moved to a
> branch about 4 metres directly above the branch it left.
>
> This was accomplished with the two or three flaps of the wing previously
> mentioned and then continuing straight up with the wings folded. It was
> like a rocket launch.
>
> What amounts of energy are required for a bird of the size and weight of a
> Rainbow Lorikeet to glide in a vertical direction?
The basic theory is easy. A Rainbow Lorikeet weighs about 0.12 kg,
gravity is 9.8ms^-2 so to raise a lorikeet 4 metres, you need 0.12*9.8*4
joules. In other words roughly 4 joules of energy. This could be
achieved by 4 watts applied for a second.
This is a minimum energy expenditure. Due to inefficiencies such as
energy lost to air turbulance, the lorikeet may have to expend several
significantly more energy. 10 joules is a safe order-of-magnitude
estimate for the amount of energy your Lorikeet expended.
Andrew
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