Calculating Average Speed: A Step-by-Step Physics Solution

This problem asks us to determine the average speed of an object that moves in two distinct segments. Average speed is a fundamental concept in physics that describes the overall rate at which an object covers distance over a period of time.

Understanding Average Speed

Average speed is defined as the total distance traveled divided by the total time taken for the entire journey. It doesn't consider the variations in speed during different parts of the journey, only the overall outcome.

The formula for average speed is:

\(\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}\)

Calculating Total Distance Traveled

The object travels in two parts:

• First part: 20 meters
• Second part: 25 meters

To find the total distance, we add the distances of these two segments:

\(\text{Total Distance} = \text{Distance}_1 + \text{Distance}_2\)

\(\text{Total Distance} = 20 \text{ m} + 25 \text{ m}\)

\(\text{Total Distance} = 45 \text{ m}\)

Calculating Total Time Taken

Similarly, the time taken for the two parts of the journey are:

• First part: 5 seconds
• Second part: 10 seconds

To find the total time, we add the times for these two segments:

\(\text{Total Time} = \text{Time}_1 + \text{Time}_2\)

\(\text{Total Time} = 5 \text{ s} + 10 \text{ s}\)

\(\text{Total Time} = 15 \text{ s}\)

Final Calculation of Average Speed

Now that we have the total distance and the total time, we can calculate the average speed using the formula:

\(\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}\)

Substitute the calculated values:

\(\text{Average Speed} = \frac{45 \text{ m}}{15 \text{ s}}\)

\(\text{Average Speed} = 3 \text{ m/s}\)

Therefore, the average speed of the object is 3 m/sec.

Analysis of Options

Let's compare our calculated average speed with the given options:

• Option 1: 5 m/sec
• Option 2: 3 m/sec
• Option 3: 4 m/sec
• Option 4: 2 m/sec

Our calculated value of 3 m/sec matches Option 2.

Revision Table: Key Concepts

Additional Information on Speed and Velocity

While average speed is the total distance divided by total time, average velocity is defined as the total displacement divided by the total time. Displacement is a vector quantity representing the change in position, whereas distance is a scalar quantity representing the total path length.

• Speed: A scalar quantity, only has magnitude (e.g., 3 m/s).
• Velocity: A vector quantity, has both magnitude and direction (e.g., 3 m/s East).
• In straight-line motion without changing direction, the magnitude of average velocity equals average speed.
• When an object changes direction, the total distance is greater than the magnitude of the displacement, and thus average speed is greater than the magnitude of average velocity.

This question focused purely on average speed, requiring only the total distance and total time.