What must exist for electric charges to flow?

Horseshoe bats (genus Rhinolophus) emit sounds from their nostrils, then listen to the frequency of the sound reflected from their prey to determine the prey's speed.

Speed is the ratio of what two measurements

This is two or more elements chemically combined in a fixed ratio. Example: water, carbon dioxide, sodium chloride

In terms of physics why should a golfer follow his or her swing

which of the following describes how the Earth's magnetic pole is related to its geographical poles? A. the magnetic poles and geographical poles are the same B. the magnetic poles vary depending on where on the Earth you are C.

If there are 20 Earthworms in a garden that covers 5 square meters, what is the population density of the earthworms? A. 20 Earthworms B. 4 C. 100 Earthworms per square meter D. 4 Earthworms per square meter

How are AC and DC generators different? In AC generators, commutators produce alternating current. In AC generators, no commutators or slip rings are used. In DC generators, slip rings produce direct current.

A 30.0-kg object experiences a drag force due to air resistance with a magnitude proportional to the square of its speed. The object falls with an acceleration of 4.00 m/s2 downward when it is falling downward at 70.0 m/s.

If a tank contains water 4 m deep, what is the pressure at the bottom of the tank? (Neglect the atmospheric pressure.)

Eli rolled a ball down the cement sidewalk as hard as he could. The ball rolled for less than a minute before it came to a stop. What force acted to slow and finally stop the ball? A.