Paragraph for Question Nos. 39 to 41 A uniform thin cylindrical disk of mass M and radius R is attached to two identical massless springs of spring constant k which are fixed to the wall as shown in the figure. The springs are attached to the axle of the disk symmetrically on either side at a distance d from its centre. The axle is massless and both the springs and the axle are in a horizontal plane. The unstretched length of each spring is L. The disk is initially at its equilibrium position with its centre of mass (CM) at a distance L from the wall. The disk rolls without slipping with velocity V0 →= V0→ i^ .The coefficient of friction is µ. Figure : 1. 39. The net external force acting on the disk when its centre of mass is at displacement x with respect to its equilibrium position is   −kx   −2kx   −2kx / 3   −4kx / 3   Hint Half-n-half Clue   2. 40. The centre of mass of the disk undergoes simple harmonic motion with angular frequency ω equal to   √ k M   √ 2k M   √ 2k 3M   √ 4k 3M   Half-n-half Clue   3. 41. The maximum value of V0 for which the disk will roll without slipping is   μg√ M k   μg√ M 2k   μg√ 3M k   μg√ 5M 2k   Half-n-half Clue