Tierra is playing in her backyard when she hears her friend calling out to her. she can't see her friend but can hear her friend's voice. which wave phenomenon explain why tierra can hear her friend even when she can't see her?

Aregion of space in which a measurable gravitational force is indicated by the force exerted on a test mass is called

The voltage applied across a given parallel-plate capacitor is doubled. how is the energy stored in the capacitor affected?

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.