Question:

A horse rider covers half the distance with $5\, m / s$ speed The remaining part of the distance was travelled with speed $10\, m / s$ for half the time and with speed $15\, m / s$ for other half of the time The mean speed of the rider averaged over the whole time of motion is $\frac{x}{7} m / s$ The value of $x$ is _____

Updated On: Mar 19, 2025
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Correct Answer: 50

Solution and Explanation

The correct answer is 50.
A horse rider covers half the distance with 5m/s speed
tAB​=\(\frac{x}{5m/s}\)
In motion BC 
x=d1​+d2​ 
where d1​&d2​ we the distance travelled with 10 m/s and 15m/s respectively in equal time intervals 
2t′​ each 
d1​=\(\frac{10t}{2}\)​,d2​=\(\frac{15t}{2}\)
d1​+d2​=x=\(\frac{t}{2}\)(10+15)=\(\frac{25t}{2}\)
v=\(\frac{2x}{\frac{x}{5}+\frac{2x}{25}}\)​=750​m/s
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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:

  1. 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.
  2. 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.