Final answer:
A person with a mass of 35.0 kg weighing 343 N is on Earth, as their weight divided by their mass equals the Earth's gravity of 9.8 m/s².
Step-by-step explanation:
To determine on which planet a person with a mass of 35.0 kg weighs 343 N, we need to use the formula weight = mass × acceleration due to gravity (g). Here, the person's weight divided by their mass gives us the acceleration due to gravity on the planet they're standing on: 343 N / 35.0 kg = 9.8 m/s². This value matches the acceleration due to gravity on Earth, so the person is standing on Earth.