question_answer 37)

A disc revolves with a speed of  and has a radius of 15 cm. Two coins are placed at 4 cm and 14 cm away from the centre of the disc. If the coefficient of friction between the coins and the disc is 0.15, which of the two coins will revolve with the disc? Take .  

Answer:

Here   The coin will revolve with the disc if the force of friction is enough to provide the necessary centripetal force, i.e.,          or Now      Thus the coin placed at a distance of 4 cm from the centre of the disc will revolve with the disc.