Question

It is estimated that the sun will exhaust all of its energy in about ten billion years. by that time,it will have radiated about 1.2x10 joules of energy. Express this amount of energy in kilojoules

Answer 1

In about 10 billion years the Sun will have radiated approximately

$1. 2\times10^{44}\,\mathrm{J}.$ One joul is equal to $10^{-3}$ kJ, so in kJ the amount of radiation will be

$1. 2\times10^{44}\cdot10^{-3}\,\mathrm{kJ} = 1. 2\times10^{41}\,\mathrm{kJ}.$