A car travels from A to B at a speed of 20,,km/hr and returns at a speed of 30,,km/hr . average spee

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2.Motion in Straight Line

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A car travels from $A$ to $ B $ at a speed of $20\,\,km/hr$ and returns at a speed of $30\,\,km/hr$. The average speed of the car for the whole journey is............$km/hr$

A

$25$

B

$24$

C

$50$

D

$5$

Solution

(b)Distance average speed$ = \frac{{2{v_1}{v_2}}}{{{v_1} + {v_2}}}$ $ = \frac{{2 \times 20 \times 30}}{{20 + 30}}$
$ = \frac{{120}}{5} = 24\;km/hr$

Standard 11

Physics

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