4. A copper kettle of mass 1 kg contains 0.9 kg of water at 15°C. It takes 12 minutes to rise the temperature to 95°C. If the electric energy is supplied at 220V, calculate the electric current, assuming 10% of heat is wasted. Given specific heat of copper = 420 J kg-K-1 and specific heat of water = 4200 J kg-1 K-1.​

Identify the correct relation showing that the radius r of the orbit of a moon of a given planet can be determined from the radius r of the planet, the acceleration of gravity at the surface of the planet, and the time τ required by the moon to complete one full revolution about the planet. determine the acceleration of gravity at the surface of the planet jupiter knowing that r = 71 492 km and that t= 3.551 days and r= 670.9 × 10^3 km for its moon europa.