Question

If a body travels 10 m distance at a speed of 10 m/s and then next 10 m distance at a speed of 20 m/s in the same direction, what is its average speed in m/s?

• A. 13
• B. 5
• C. \( \frac{40}{3} \)
• D. \( \frac{50}{3} \)

Hint:

The average speed is the total distance divided by the total time. Use this formula for cases where different speeds are involved over equal distances.

Answer 1

The Correct Option is C

Step 1: Formula for average speed.
The average speed \( v_{avg} \) is given by: \[ v_{avg} = \frac{\text{Total Distance}}{\text{Total Time}}. \]
Step 2: Calculate total distance.
Total distance = \( 10 + 10 = 20 \) m.
Step 3: Calculate total time.
Time taken to cover the first 10 m at 10 m/s: \[ t_1 = \frac{10}{10} = 1 \, \text{s}. \] Time taken to cover the next 10 m at 20 m/s: \[ t_2 = \frac{10}{20} = 0.5 \, \text{s}. \] Total time = \( 1 + 0.5 = 1.5 \, \text{s} \).
Step 4: Calculate average speed.
\[ v_{avg} = \frac{20}{1.5} = \frac{40}{3} \, \text{m/s}. \]
Step 5: Conclusion.
Thus, the average speed is \( \frac{40}{3} \) m/s, which corresponds to option (C).