AP EAMCET202124 Aug 2021Morning ShiftPhysicsMotion in One DimensionActual
A train travels from city- A to city- B with a constant speed of 18 ~ms ⁻¹ and returns back to city- A with a constant speed of 36 ~ms ⁻¹ . Find its average speed during the journey.
Options
- A72 5 ~ms ⁻¹
- B36 3 ~ms ⁻
- C72 3 ~ms ⁻¹
- D36 5 ~ms ⁻¹
Correct answer
C. 72 3 ~ms ⁻¹
Step-by-step solution
Given that, speed of train from city- A to city- B , v₁=18 ~m / s Speed of train from city- B to city- A v₂=36 ~m / s In this process, the distance travelled by train from A to B and B to A will be equal. Now, using the expression of average speed for equal distance, we know v_ a v = 2 v₁ v₂ v₁+v₂ By substituting the values, we get aligned v_ a v & = 2 18 36 18+36 & = 2 36 18 54 = 72 3 ~m / s aligned