Question:
A boy walks to his school at a distance of 6 km with constant speed of ${2.5\, km \, h^{-1}}$ and walks back with a constant speed of ${4\, km \, h^{-1}}$. His average speed for round trip expressed in ${ km \, h^{-1}}$, is
A boy walks to his school at a distance of 6 km with constant speed of ${2.5\, km \, h^{-1}}$ and walks back with a constant speed of ${4\, km \, h^{-1}}$. His average speed for round trip expressed in ${ km \, h^{-1}}$, is
Updated On: Jun 7, 2022
- $ \frac{24}{13}$
- $ \frac{40}{13}$
- 3
- $ \frac{1}{2}$
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The Correct Option is B
Solution and Explanation
Total times $t = \frac{6}{2.5} + \frac{6}{4} = \frac{12}{5} + \frac{3}{2} = \frac{39}{10} h$
Average speed, $v ={ \frac{6+6}{39/10} = \frac{120}{39} = \frac{40}{13} km \, h^{-1}}$
Average speed, $v ={ \frac{6+6}{39/10} = \frac{120}{39} = \frac{40}{13} km \, h^{-1}}$
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Concepts Used:
Motion in a straight line
The motion in a straight line is an object changes its position with respect to its surroundings with time, then it is called in motion. It is a change in the position of an object over time. It is nothing but linear motion.
Types of Linear Motion:
Linear motion is also known as the Rectilinear Motion which are of two types:
- Uniform linear motion with constant velocity or zero acceleration: If a body travels in a straight line by covering an equal amount of distance in an equal interval of time then it is said to have uniform motion.
- Non-Uniform linear motion with variable velocity or non-zero acceleration: Not like the uniform acceleration, the body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. The rate of change of its velocity changes at different points of time during its movement.