Suppose that, while lying on a beach near the equator watching the sun set over a calm ocean, you start a stopwatch just as the top of the sun disappears. you then stand, elevating your eyes by a height h= 1.70 m, and stop the watch when the top of the sun again disappears. if the elapsed time is 11.1 s, what is the radius r of earth?

When a book falls from a shelf to the ground without anyone pushing on it, no work is done on the book. true or false

Suppose that an electromagnetic wave which is linearly polarized along the x−axis is propagating in vacuum along the z−axis. the wave is incident on a conductor which is placed at z > 0 region of the space. the conductor has conductivity σ, magnetic permeability µ and electric permittivity ε. (a) find the characteristic time for the free charge density which dissipates at the conductor. (b) write the maxwell equations and derive the wave equation for a plane wave propagating in a conductor. (c) find the attenuation distance at which the incident amplitude reduces to e ^−1 of its initial value. (d) find the electric and magnetic fields inside the conductor. 8 (e) find the power loss per area of the incident electromagnetic wave at the surface of conductor.

Which safety measures should you follow during a thunderstorm? check all that apply. (a) avoid touching anything that conducts electricity. (b) avoid touching a person who has been struck by lightning. (c) go outside. (d) keep your computer turned off. (e) stay out of water. (f) stay inside.