Is aluminum foil reflecting onto something conduction, convection, or radiation? (this is for science sorry if i chose the wrong catagory I don't know the fancy word for science)

An object of dimensions 50 cm x 40 cm x 0.20 cm has a mass 60g. find its density in g/cm3 and kg/ m3

What is part of a line has one endpoint and continues in one direction?

Three resistors are connected in series across a 15-v power supply. if the potential drops across resistors 1 and 2 are 4.1 volts and 3.1 volts, what is the exact potential drop (in volts) across resistor 3?