Q4. A thin circular disc of mass $M$ and radius $R$ is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with angular velocity $\omega$. If another disc of same dimensions but of mass $\mathrm { M } / 2$ is placed gently on the first disc co-axially, then the new angular velocity of the system is :
(1) $\frac { 3 } { 2 } \omega$
(2) $\frac { 5 } { 4 } \omega$
(3) $\frac { 2 } { 3 } \omega$
(4) $\frac { 4 } { 5 } \omega$
Q5.
[Figure]A block is simply released from the top of an inclined plane as shown in the figure above. The maximum compression in the spring when the block hits the spring is :
(1) $\sqrt { 6 } \mathrm {~m}$
(2) $\sqrt { 5 } \mathrm {~m}$
(3) 1 m
(4) 2 m