Question

35. A boy is walking due east with speed 6m/s. He is
whirling a ball tied to a thread in horizontal circle
with angular velocity" w" =3 rad/s (in anti-clockwise
direction as seen from top).If length of thread is 2m,
the speed of ball when it is exactly south of the boy
is
the
(1) 6 m/s
(2) 12 m/s
(3) 62 m/s (4)0m/s​

Answer 1

Answer:

Option (2) 12 m/s

Explanation:

In the frame of reference of boy, the angular velocity is

$\omega=3$ rad/s

The radius of the horizontal circle

$r=2$ m

When the ball is on the south of the boy, the linear velocity of the ball w.r.t. the boy will be in east direction because the ball is rotated anticlockwise

Therefore the linear velocity w.r.t. the boy

$v=r\omega$

$\implies v=2\times 3$

$v=6$ m/s

But the boy is also moving with speed 6 m/s in the east direction

Therefore speed of the ball

$=6+6$

$=12$ m/s

Therefore, option (2) is correct.