Question

A balloon travels upward at 1.0 m/s for half of the distance of its trip. It moves upward at 2.0 m/s for the other half of the distance of its trip. The balloon's average speed for the entire trip is :

• A. 1.5 m/s
• B. less than 1.5 m/s
• C. greater than 1.5 m/s
• D. 0 m/s
• E. Not enough information is given to answer this question.

Answer 1

The correct option is B less than 1.5 m/s

Given : $v_1=1$ m/s $v_2=2$ m/s

Let the distance covered in each half be $x$.

Time taken in first half $t_1=\frac{x}{v_1}=\frac{x}{1}$ s

Time taken in 2nd half $t_2=\frac{x}{v_2}=\frac{x}{2}$ s

Total time taken $T=x+\frac{x}{2}=1.5x$ s

Average speed = $\frac{Totaldistance}{Totaltime}=\frac{2x}{1.5x}=1.33$ m/s

Hence option B is correct.