Question

Two particle starting from a point on a circle of radius 4 m in horizontal plane move along the circle with constant speed of 4 ms${}^{-1}$ and 6 ms${}^{-1}$ respectively in opposite direction .The paticles will collide with each other after a time of

• A. $3.0s$
• B. $2.5s$
• C. $2.0s$
• D. $1.5s$

Answer 1

The correct option is B $2.5s$

circumference of circle$=2\pi r=8\pi$

Let the distance traveled by them be d and D respectively. So we know that

$d+D=10\pi .------1$

Let the time between start and collision be t. Then we know that

$d=4t$ and $D=6t$

substituting into the first equation

$10t=8\pi$

$t=\frac{8\pi }{10}$

$t=\frac{25.12}{10}$

$t=2.5sec$