Question

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

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

Answer 1

The correct option is B Less than $1.5m/s$

Let $s$ be the total distance of the trip.

Time taken to travel the first half=$\frac{s/2}{1}$

Time taken to travel the other half=$\frac{s/2}{2}$

$⟹$ total time taken=$\frac{s}{2}+\frac{s}{4}=\frac{3s}{4}$

Hence the average speed=$\frac{Totaldistancecovered}{Totaltimetaken}$

$=\frac{s}{3s/4}=\frac{4}{3}m/sec$