Why is alternating current more effective at long–distance travel than direct current?
the power lines are made out of conductors.
transformers increase or decrease voltage as needed.
the ac generator is more efficient.
ac has lower voltage than dc.

If you are using PLATO, which I'm sure you are cause I've had the same question, the answer it the following:

Transformers increase and decrease voltage as needed.

he made 11 calls in one day

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.