Final answer:
The weight of the full fish tank is 98 Newtons, calculated by adding the mass of the tank and water and multiplying by the acceleration due to gravity.
Step-by-step explanation:
The weight of the fish tank when full is calculated by summing the mass of the empty fish tank and the mass of the water it contains, and then multiplying by the acceleration due to gravity. The mass of the empty tank is given as 3kg, and the mass of the water is 7kg, totaling 10kg for the full tank. Since the acceleration due to gravity (g) is approximately 9.8 m/s2, the weight of the full fish tank W is calculated using the formula W = mg, which gives us 10kg × 9.8 m/s2 = 98N. Therefore, the fish tank when full would have a weight of 98 Newtons.