| For what it’s worth, I asked it the following: Q: Which weighs more on earth: 100kg of steel or a 100kg polystyrene ball? Be as technically correct as possible A:
Technically, 100 kg of steel and 100 kg of polystyrene weigh the same on Earth when measured on a scale, as they both experience the same gravitational force due to their equal mass. However, there are some nuances to consider: Buoyancy Effect Earth’s atmosphere exerts an upward buoyant force on objects, proportional to the volume of the object and the density of the surrounding air. Since polystyrene has a much lower density than steel, a 100 kg polystyrene ball will have a significantly larger volume and experience a greater buoyant force compared to 100 kg of steel. As a result:
• Effective weight (apparent weight): The steel will weigh slightly more than the polystyrene on a scale because the buoyant force acting on the polystyrene reduces its apparent weight more. Actual Weight Weight is the gravitational force on an object and is given by: Where and . Without considering buoyancy, both objects have the same weight of approximately (newtons). Conclusion
• True weight (in a vacuum): Both are identical at 981 N.
• Apparent weight (in air): Steel is slightly heavier due to reduced buoyant force acting on it compared to the polystyrene ball. |
They very often get popular "tricky" questions wrong because they saw it so many times that they switch from internal reasoning to memorization/retrieval.