In a children’s park a heavy rod is pivoted at the center and is made to rotate about the pivot so that the rod always remains horizontal. Two kids hold the rod near the ends and thus rotate with the rod (figure 7-E2). Let the mass of each kid be 15 kg, the distance between the points of the rod where the two kids hold it be 30 m and suppose that the rod rotates at the rate of 20 revolutions per minute. Find the force of friction exerted by the rod on one of the kids.
If the length of the rod is l then the centrifugal force on one of the kids will be,
The force of gravity is balanced by the normal reaction force. Due to its rotating motion centrifugal force will act outwards. But to keep the boys stuck friction must balance the centrifugal force.
The system swipes 40∏ angle in a minute. So, the angular velocity will be,
The friction force will be,
