The ceiling of a single-family dwelling in a cold climate should have an R-value of 49 ft2 ·F°·h/Btu. To give such insulation, how thick would a layer of (a) polyurethane foam and (b) silver have to be? The thermal conductivity of polyurethane foam is 0.024 W/m·K, and the thermal conductivity of silver is 428 W/m·K.

Apositive rod is placed to the left of sphere a, and the spheres are separated. which best describes the spheres? sphere a is negative and sphere b is positive because protons from sphere a are attracted to the rod and move to sphere b. sphere a is negative and sphere b is positive because electrons from sphere b are attracted to the rod and move to sphere a. sphere a is positive and sphere b is negative because electrons from the rod move to sphere b and protons then move to sphere a. sphere a is positive and sphere b is negative because protons move from sphere b to the rod and also to sphere a.

Explain what it means to view something from a frame of reference. provide an example that illustrates your explanation. (4 points)

Aspectroscope breaks light up into its colors, allowing scientists to analyze light from the solar system and universe. by studying the spectral line patterns, widths, strengths and positions, scientists can determine the speed, position, and of celestial bodies. a) age b) origin c) rotation d) temperature