Q. A car travels equal distances in the same direction with velocities $60kmh^{- 1}$, $20\ km\ h^{- 1}$ and 10 $km\ h^{- 1}$respectively. The average velocity of the car over the whole journey of motion is
A) $8\ ms^{- 1}$
B) $7\ ms^{- 1}$
C) $6\ ms^{- 1}$
D) $5\ ms^{- 1}$
Explanation
(d) Average velocity$= \frac{3x}{\frac{x}{60} + \frac{x}{20} + \frac{x}{10}} = \frac{3x}{\frac{x + 3x + 6x}{60}}$
$= \frac{3x \times 60}{10x} = 18kmh^{- 1}$
$= \frac{18 \times 5}{18}ms^{- 1} = 5ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.