Suppose a vacuum cleaner use 120 j of electrical energy. if 45 j are used to pull air into the vacuum cleaner, how efficient is the vacuum cleaner?

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.

Compare the patterns of the two waves shown in the image. which statement is true about these waves?

Based on the image below what would an observer on the nighttime side of earth observe?