Q123 / 180 · KCET 2014 · Physics

A car moves from A to B with a speed of \( 30 \mathrm{kmph} \) and from B to A with a speed of \( 20 \mathrm{kmph} \).
What is the average speed of the car ?

  • A
    \( 25 \mathrm{kmph} \)
  • Correct answer
    B
    \( 24 \mathrm{kmph} \)
  • C
    \( 50 \mathrm{kmph} \)
  • D
    \( 10 \mathrm{kmph} \)

Solution

Given, speed of car from $\mathrm{A}$ to $\mathrm{B}=30 \mathrm{kmph}^{-1}=v_{1}$ Speed of car from $\mathrm{B}$ to $A=20 \mathrm{~km} h^{-1}=v_{2}$ Average speed of car $=\frac{2 v_{1}+v_{2}}{v_{1}+v_{2}}=\frac{2 \times 30 \times 20}{30+20}=\frac{1200}{50}=24$ Average speed of car $=24 \mathrm{kmph}$

Hence, the correct answer is option: 'B'.

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