Question

4. A ball rotates at a rate r rotations per second and
simultaneously revolves around a stationary point O at
a rate R revolutions per second (R<r). The rotation and
revolution are in the same sense. A certain point on the
ball is in the line of the centre of the ball and point O at
a certain time. This configuration repeats after a time.
1 1
(A)
(B)
Rr
1
1 1
(C)
(D)
r+R
1
r - R
+
RI​

Answer 1

Answer:

I have no idea what to do in this question

Answer 2

Step-by-step explanation:

As rotation and revolution are both in the same direction (say, counterclockwise), the point will come in the line connecting centers after one complete rotation. Say that happens after part revolution of angle θ against one full revolution (2π). In that time the rotation has completed by (2π+θ) (more than one rotation of (2π).

One rotation takes 1r second and one revolution takes 1R second. Equating the time taken -

2π+θ2πr=θ2πR

Now please find θ and then plug in either Right Hand side or in Left Hand side to find the time.