3. Two people stand facing each other 200 m apart on one side of a high
wall and at the same perpendicular
distance from it. When one fires a
pistol, the other hears a report 0.6
seconds after the flash and a second
sound 0.25 seconds later. Explain this
and calculate:
(a) Velocity of sound in air
(b) Perpendicular distance of the
people from the wall.​

With the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 1.90

Which lists the pairs of plates in order from least to greatest in terms of the work done to move the electron?

An electromagnet is a device in which moving electric chargers in a coil of wire create a magnet. whats one advantage of using electromagnetic in devices