On Mon, 17 Aug 2009 20:42:46 -0700, Winston
wrote:

Pete C. wrote:
Winston wrote:

(...)

She should be able to get 10 A at 120 V out of a 14 AWG
extension cord measuring 75' in length. So that's 1200 W
or 1.6 HP. My little 30cc brush cutter does an acceptable
job with only 1.0 HP, so it isn't unreasonable to ask for
an A.C. brush cutter, is it?

Factor in voltage drop and motor efficiency and you'll be lucky to get
even close to 1 real HP.

Electric motors generally exceed 80% efficiency.
Gas motors rarely exceed 25% efficiency.

Figure less than 6 V drop for a 75 foot extension cord
at 15A and less than 4 V drop at 10A.
120 - 6 = 114 V. That'd work great!

--Winston

Your calculations are way off. First there is the length of the house
wiring from the service entrance to wherever you plug in the extension
cord. Then there is the cord itself and loss at connections which are
rarely perfect. If the combined total length of the house wiring and
the extension is more than 50 feet, you need to get a MUCH heavier
extension cord. 14AWG is not going to cut it. Go to a 10 AWG if you
want the power at the outlet to arrive at the tool. Unfortunately,
your diminuative friend will need a wheelbarrow to move that extension
cord.