Question

A person is running along a circular track of area 625 π m2 with a constant speed. Find the displacement in 15 seconds if he has ti complete the race in 30 seconds.

Answer 1

Answer:

Explanation: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

Answer 2

Answer:50 m

Explanation:

Area of the circle = 625 π m²

Also, Area of Circle = π r²

Equating,  π r² = 625 π

∴  r² = 625

    r = 25 m.

The person cover the entire perimeter in 30s. So, he will cover half the distance in 15 s.  But, Displacement is the shortest distance between the initial and the final point, which is the diameter in this case.

So the displacement in 15s is the diameter of the circle.

diameter = 2 * radius = 2 * 25  =  50 m.