To determine the average speed of the car during its journey, we can use the formula for average speed, which is defined as the total distance traveled divided by the total time taken. ### Step-by-Step Explanation 1. **Identify the Total Distance**: The car travels a total distance of 150 kilometers to the east. 2. **Identify the Total Time**: The time taken for this journey is 2 hours. 3. **Use the Average Speed Formula**: The formula for average speed (v) is given by: \[ v = \frac{\text{Total Distance}}{\text{Total Time}} \] 4. **Substitute the Values**: Plugging in the values we have: \[ v = \frac{150 \text{ km}}{2 \text{ hours}} \] 5. **Perform the Calculation**: Now, we perform the division: \[ v = 75 \text{ km/h} \] Thus, the average speed of the car during this journey is **75 km/h**. ### Why Option A is Correct - **Correct Calculation**: The calculation shows that the average speed is indeed 75 km/h, which matches option A. - **Understanding Average Speed**: Average speed is a measure of how fast something is moving over a period of time, and in this case, it accurately reflects the car's journey. ### Why Other Options are Incorrect - **Option B (150 km/h)**: This option suggests that the car traveled 150 kilometers in just 1 hour. However, since the journey took 2 hours, this option is incorrect. - **Option C (300 km/h)**: This option implies that the car would have traveled 300 kilometers in 1 hour, which is not possible given the distance of 150 kilometers over 2 hours. This is an unrealistic speed for a car. - **Option D (60 km/h)**: This option suggests a slower average speed than what was calculated. If the car were traveling at 60 km/h, it would take longer than 2 hours to cover 150 kilometers, making this option incorrect. ### Common Pitfalls - **Misunderstanding Average Speed**: Some students may confuse average speed with instantaneous speed, which is the speed at a specific moment in time. - **Incorrectly Dividing Distance by Time**: Ensure that the units are consistent (kilometers and hours) when performing the calculation. - **Ignoring Direction**: While the problem states the direction (east), average speed is a scalar quantity and does not depend on direction. However, students might mistakenly think direction affects average speed. ### Revision Summary - Average speed is calculated using the formula: \( v = \frac{\text{Total Distance}}{\text{Total Time}} \). - For this problem, the average speed of the car is 75 km/h. - Always ensure units are consistent when calculating speed. - Average speed is a scalar quantity and does not consider direction. By understanding these concepts and practicing similar problems, you can confidently tackle questions related to average speed in physics.