What is the first stage in a star's lifecycle when dust and gas begin to come together?

What are similarities and differences of reflection, refraction, diffraction and absorption?

Does anyone have the answers to online physics course plato course physics, semester a v3.0

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.