A block of mass $1 kg$ is pushed up a surface inclined to horizontal at an angle of 30" by a force of $10\mathrm{N}$ parallel to the inclined surface (figure). The coefficient of friction between block and the incline is $0.1 .$ If the block is pushed up by $10\mathrm{m}$ along the incline, calculate

(e) work done by applied force.

A curved surface is shown in figure. The portion $BCD$ is free of friction. There are three spherical balls of identical radii and masses. Balls are released from rest one by one from A which is at a slightly greater height than $C$. With the surface $AB$, ball $1$ has large enough friction to cause rolling down without slipping; ball $2$ has a small friction and ball $3$ has a negligible friction.

(a) For which ball is total mechanical energy conserved?

A curved surface is shown in figure. The portion $BCD$ is free of friction. There are three spherical balls of identical radii and masses. Balls are released from rest one by one from A which is at a slightly greater height than $C$. With the surface $AB$, ball $1$ has large enough friction to cause rolling down without slipping; ball $2$ has a small friction and ball $3$ has a negligible friction.

(b) Which ball $\left(s\right)$ can reach $D$?

A curved surface is shown in figure. The portion $BCD$ is free of friction. There are three spherical balls of identical radii and masses. Balls are released from rest one by one from A which is at a slightly greater height than $C$. With the surface $AB$, ball $1$ has large enough friction to cause rolling down without slipping; ball $2$ has a small friction and ball $3$ has a negligible friction.

(c) For balls which do not reach $D$, which of the balls can reach back $A$ ?