Question

The first half of total distance of 50 km is covered in 2 h, and the second half in 3 h. The average speed is ______.

• A. 2.78 ms^ (-1)
• B. 7 ms^ (-1)
• C. 13.8 ms^ (-1)
• D. 5.56 ms^ (-1)

Answer 1

The correct option is A 2.78 ms^ (-1)

Given:
The total distance, $d=50\text{km}$
Total time, $T=2h+3h=5h$

Average speed, $v_{avg}=\frac{d}{T}=\frac{50\text{km}}{5\text{h}}$
$⟹v_{avg}=10\text{kmph}$

Also $1km=1000m$, $1\text{h}=60\text{min}=3600\text{s}$
$⟹10\text{kmph}=\frac{10\times 1000}{3600}\text{m}{\text{s}}^{-1}$
$=\frac{25}{9}\text{m}{\text{s}}^{-1}=2.78m{s}^{-1}$
$\therefore v_{avg}=2.78\text{m}{\text{s}}^{-1}$