Question

An athlete completes one round of a circular track of radius 10m in 40 sec. Find the distance covered by him in 2 min 20 sec.
A. 70 m
B. 140 m
C. 110 m
D. 220 m

Answer 1

Hint: In order to solve this problem we need to know about revolution. When an object goes around the center of the axis in a circular path is known as revolution. Distance is defined as the product of the revolution and the circumference of a circle.

Formula Used:
To find the number of revolutions the formula is given by,
Number of revolutions = total time/time taken

Complete step by step solution:
When an athlete completes one round of a circular track with a radius 10m in 40 sec. then we need to find the distance covered by him in 2 min 20 sec. To find the number of revolutions the formula is given by,
Number of revolutions = total time/time taken

Number of revolutions is defined as the ratio of total time by time period, that is,
Number of revolutions \[ = \dfrac{{140}}{{40}}\]
Total time is, 2min 20sec is 140sec
Number of revolutions \[ = 3.5\]
So, the distance can be given as,
$\text{Distance}$ = number of revolution $\times$ circumference of circle
\[\text{Distance} = 3.5 \times 2\pi R\]
Substitute the value of \[R = 10m\] then,
\[\text{Distance} = 3.5 \times 2 \times 3.142 \times 10\]
\[\therefore \text{Distance} = 220\,m\]
Therefore, the distance covered by him in 2 min 20 sec is 220 m.

Hence, option D is the correct answer.

Note: Here in the given problem it is important to remember that the equation for the revolution and also the distance travelled by the athlete in a circular path. Using this we can easily get the solution.