The correct option is **C. Force**. ### Detailed Explanation In the International System of Units (SI), quantities are classified into two main categories: **base quantities** and **derived quantities**. 1. **Base Quantities**: These are the fundamental physical quantities from which other quantities can be derived. The seven base quantities in the SI system are: - Length (meter, m) - Mass (kilogram, kg) - Time (second, s) - Electric current (ampere, A) - Thermodynamic temperature (kelvin, K) - Amount of substance (mole, mol) - Luminous intensity (candela, cd) 2. **Derived Quantities**: These are quantities that are derived from the base quantities through mathematical relationships. They are expressed in terms of the base quantities. Examples of derived quantities include: - Area (square meters, m²) - Volume (cubic meters, m³) - Speed (meters per second, m/s) - Acceleration (meters per second squared, m/s²) - Force (newton, N) ### Why Force is a Derived Quantity Force is defined by Newton's second law of motion, which states that force is the product of mass and acceleration. The formula for force is given by: \[ F = m \cdot a \] Where: - \( F \) is the force in newtons (N), - \( m \) is the mass in kilograms (kg), - \( a \) is the acceleration in meters per second squared (m/s²). From this formula, we can see that force is derived from the base quantities of mass and acceleration. Since acceleration itself is derived from the base quantities of length and time (as acceleration is the change in velocity over time), force is indeed a derived quantity. ### Why the Other Options are Incorrect - **A. Length**: Length is a base quantity in the SI system. It is measured in meters (m) and does not depend on any other quantities for its definition. - **B. Mass**: Mass is also a base quantity in the SI system. It is measured in kilograms (kg) and is fundamental to the measurement of matter. - **D. Time**: Time is another base quantity in the SI system, measured in seconds (s). It is a fundamental aspect of the physical universe and does not derive from other quantities. ### Common Pitfalls - Confusing derived quantities with base quantities is a common mistake. Remember that derived quantities are formed from combinations of base quantities. - Not recognizing that some quantities, like force, depend on multiple base quantities can lead to misunderstandings in physics problems. ### Revision Summary - **Base quantities** in the SI system include length, mass, and time, which are fundamental and do not derive from other quantities. - **Derived quantities** are formed from base quantities; force is a prime example, derived from mass and acceleration. - The formula for force is \( F = m \cdot a \), illustrating its dependence on base quantities. - Always differentiate between base and derived quantities to avoid confusion in physics concepts.