Which of the following best defines weight, and what is its SI unit?

• A. Weight is the amount of matter in an object; its SI unit is kilogram (kg).
• B. Weight is the force exerted by gravity on an object; its SI unit is newton (N).
• C. Weight is the volume occupied by an object; its SI unit is cubic meter (m^3).
• D. Weight is the energy possessed by an object; its SI unit is joule (J).

Answer: (B)

Verified step by step guidance

1. Understand that weight is a force, which means it depends on both the mass of an object and the acceleration due to gravity acting on it.
2. Recall the formula for weight: \(\\text{Weight} = m \\times g\), where \(m\) is the mass of the object and \(g\) is the acceleration due to gravity (approximately \$9.8 \\; m/s^2$ on Earth).
3. Recognize that since weight is a force, its SI unit must be the unit of force, which is the newton (N).
4. Differentiate weight from mass, volume, and energy: mass is the amount of matter (kg), volume is the space occupied (m\(^3\)), and energy is the capacity to do work (joule, J).
5. Conclude that the best definition of weight is 'the force exerted by gravity on an object' and its SI unit is the newton (N).