Question

A person is running along a circular track of area 625 pie metre square with a constant speed. Find the displacement in 15 seconds if he has to complete the race in 30 seconds

Answer 1

Find the radius:

Area = πr²

πr² = 625π

r² = 626

r² = √625

r = 25 m

Find the circumference:

Circumference = 2πr

Circumference = 2π(25) = 50π m

Find the distance the person covered in 1 second:

30 seconds = 50π

1 second = 50π ÷ 30 = 5π/3 m

Find the distance the person covered in 15 second:

1 second = 5π/3 m

15 seconds = 5π/3 x 15 = 25π m

Answer: He completed 25π m in 15 seconds

Answer 2

Answer

The displacement in 15 seconds  = 25π

Explanation

Step 1: Find the radius of circular track

It is given that,

A person is running along a circular track of area 625 pie metre square with a constant speed.

Area, A =  π$r^{2}$ = 625

             Therefore , radius r = 25m

Step 2: Find the circumference of circular track

     circumference  2 π r =2x πx 25

Step 3: Find the  displacement in 15 seconds

He need to  complete the race in 30 seconds in constant speed means,

complete  2x π x 25 m  distance in 30 seconds.

The displacement in 15 seconds  =  (2x p x 25)/2 = 25π