The correct option is **C. Temperature**. ### Detailed Explanation To understand why temperature is a scalar quantity, we first need to define what scalar and vector quantities are: - **Scalar Quantities**: These are quantities that are fully described by a magnitude (numerical value) alone. They do not have a direction associated with them. Examples include mass, temperature, speed, and energy. - **Vector Quantities**: These are quantities that have both a magnitude and a direction. Examples include velocity, acceleration, and force. Now, let's analyze each option: **A. Velocity**: - Velocity is a vector quantity because it describes both how fast an object is moving (magnitude) and the direction in which it is moving. For example, if a car is traveling at 60 km/h to the north, both the speed (60 km/h) and the direction (north) are necessary to fully describe the velocity. **B. Acceleration**: - Acceleration is also a vector quantity. It indicates how quickly an object’s velocity is changing and in which direction. For instance, if a car accelerates at 5 m/s² to the east, it has both a magnitude (5 m/s²) and a direction (east). **C. Temperature**: - Temperature is a scalar quantity. It is described solely by a numerical value (e.g., 25 degrees Celsius) and does not have a direction. When we say the temperature is 25°C, we are only providing a magnitude without any directional component. **D. Force**: - Force is a vector quantity because it has both magnitude and direction. For example, if a force of 10 N is applied to the right, it is necessary to specify both the strength of the force (10 N) and the direction (to the right) to fully describe it. ### Summary of Why Other Options are Incorrect - **Velocity (A)**: Incorrect because it has both magnitude and direction. - **Acceleration (B)**: Incorrect because it also has both magnitude and direction. - **Force (D)**: Incorrect because it is defined by both magnitude and direction. ### Common Pitfalls - Students often confuse scalar and vector quantities, especially when they are familiar with the concept of speed (which is scalar) versus velocity (which is vector). Remember that speed is the magnitude of velocity. - Another common mistake is to think that any physical quantity that can be measured is a scalar. Always check if the quantity has a directional component. ### Formulas and Concepts - **Scalar Example**: Temperature (T) can be expressed in degrees Celsius (°C), Kelvin (K), or Fahrenheit (°F). - **Vector Example**: Velocity (v) can be expressed as \( v = \frac{d}{t} \) where \( d \) is displacement (a vector) and \( t \) is time (a scalar). ### Revision Summary - Scalar quantities have only magnitude; examples include temperature and mass. - Vector quantities have both magnitude and direction; examples include velocity and force. - Temperature is a scalar because it does not involve direction. - Always differentiate between scalar and vector quantities to avoid confusion in physics problems.