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 meter, m²) - Volume (cubic meter, m³) - Speed (meter per second, m/s) - Acceleration (meter 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: \[ F = m \cdot a \] 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 equation, 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 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 is one of the fundamental dimensions from which other quantities are derived. - **B. Mass**: Mass is also a base quantity in the SI system. It is measured in kilograms (kg) and serves as a fundamental measure of the amount of matter in an object. - **D. Time**: Time is another base quantity in the SI system. It is measured in seconds (s) and is fundamental to the measurement of various physical phenomena. ### 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** are fundamental and include length, mass, and time. - **Derived quantities** are formed from base quantities; force is a prime example. - Force is calculated using the formula \( F = m \cdot a \), linking mass and acceleration. - Always differentiate between base and derived quantities to avoid confusion in physics.