Question

Two particles start moving from the same position on a circle of radius 20 cm with speed 45 metre per second and 36 m per second respectively in the same direction find the time after which the particles will meet again

Answer 1

The first thing is to get the circumference of the circular path.

Circumference = 3.142 × 2 × 20 = 125.68 cm

We can divide this by 100 to get it in meters.

125.68/100 = 1.2568m

Time = Distance / Speed

The time taken by each to go round is :

First particle = 1.2568/45 = 0.0279 Seconds

Second particle = 1.2568/36 = 0.0349

We round off to three decimal places each.

Particle A = 0.028 s

Particle B = 0.035 s

To get the time they will meet again, we should find the LCM of the two times.

Their LCM is :

140/1000 = 0.14

So they will meet after approximately 0.14 seconds

Answer 2

Relative Speed = 40π - 36π= 4π rad/s

Circumference = 2π × 0.2 = 0.4π rad

Time taken to meet again = circumference/ relative speed = 0.4π/4π = 0.1 s