The ceiling of a single-family dwelling in a cold climate should have an r-value of 46 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.

The atoms in a nickel crystal vibrate as harmonic oscillators with an angular frequency of 2.3 × 1013 rad/s. the mass of a nickel atom is 9.75 × 10-26 kg. what is the difference in energy between adjacent vibrational energy levels of nickel? (h = 6.626 × 10-34 j • s, , 1 ev = 1.60 × 10-19 j)

22. the top of a cliff is located a distance h above the ground. at a distance h/2 there is a branch that juts out from the side of the cliff, and on this branch a bird's nest is located. two children throw stones at the nest with the same initial speed, one stone straight downward from the top of the cliff and the other stone straight upward from the ground. in the absence of air resistance, which stone hits the nest in the least amount of time?

It is advised not to hold the thermometer by the bulb while reading it