The downward acceleration of a falling body on earth is 9.81m/s2. on the moon the same quantity is 1.62m/s2. an astronaut in a space suit has a mass of 145kg. (a) what is the astronaut’s weight on earth? (b) on the moon? (c) what is the astronaut’s mass on the moon?

The astronaut's mass doesn't change.  It's the same wherever he goes,
because it doesn't depend on what else is around him.

His weight depends on what else is near him, so it changes, depending
on where he is.

         Weight  =  (mass) x (gravity)

On Earth,  Weight = (145 kg) x (9.81 m/s²)  =  1,422.5 newtons.
                                                               (about 320 pounds)

On the moon, Weight = (145 kg) x (1.62 m/s²)  =  234.9 newtons.
                                                                   (about 53 pounds)

The answer is orbit around nucleus

The radiation of the fire causes the saucepan to heat up. the conduction of the saucepan then to distribute the heat over the saucepan and to give heat to the water. the convection of the water distributing the heat within the water, till all the water is boiling