Which of the following statements about stars is true? a. none of these b. all stars are the same size. c. stars vary greatly in size. d. stars rarely differ in size.

The transfer of heat through the movement of a gas or liquid a. convection b. conduction c. radiation

Consider a 1000 w iron whose base plate is made of 0.5 cm thick aluminum alloy 2024-t6 (ρ = 2770 kg/m3 and cp = 875 j/kg°c). the base plate has a surface area of 0.03 m2. initially, the iron is in thermal equilibrium with the ambient air at 22°c. assuming 90% of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200°c.

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?