On Mar 19, 1:18*am, The Real Doctor wrote:
On 18 Mar, 22:59, Darryl Ramm wrote:

On Mar 18, 3:34*pm, Jim Logajan wrote:

The Real Doctor wrote:

On 18 Mar, 01:38, Darryl Ramm wrote:

As I explained, Gravity provides the energy...

Then you will need to explain how gravity provides the energy when the
glider is climbing.

Just curious, but are you being pedantic?

Just an extreme case of rasterbation. If he keeps it up he will go
blind.

Go on then. Explain how "gravity provides the energy" when a glider is
climbing ...

Ian


A glider "climbs" when you pull back on the stick and converts kinetic
energy to gravitational potential energy, but that does not get you
far since you can't create within that closed system. The glider also
"climbs" - (maybe you should think of "lifted" if "climb" confuses
you) by a rising air mass and that does increase the glider's
gravitational potential energy. You can then utilize that energy to go
places. There is no other coupling between raising air and the glider
somehow magically using that to get energy go places. Are you confused
by the case of flying in zero sink? That's no different the raising
air just happens to match the sink rate, gravity is still required/is
the coupling mechanism. And a glider while being lifted in a thermal
or wave etc. is still expending gravitational potential energy to
maintain forward flight, it's just being lifted faster than it
descends.

Replace drag with the effort of running, and potential energy with
kinetic (but it lets me invoke chickens again).... If a chicken runs
backwards in a stationary train it is expending a certain amount of
energy (glider sinking in still air). As the train picks up speed and
exceeds the chicken's speed the net speed of the chicken moves forward
(glider is now being lifted in lift), and the chicken gains an
increase in net energy however the chicken is still expending the same
energy to walk to the back of the train (the glider is still using
gravitational potential energy to fly). Don't like that, think of a
ball rolling down an infinitely long inclined ramp and the ramp being
raised faster than the ball falls. What way does the ball move? to an
observer on the ground? Is the ball giving up gravitational potential
energy to slide down the ramp relative to an observer on the ramp?
(yes). Is the ball gaining net energy? (yes).


So how many ways do people need to keep answering the same pedantic
question you keep asking? Do the ultimate thought experiment, turn off
gravity and the glider will just float along with moving air currents
but will be unable to glide anywhere.


Darryl