Question

A curved surface is shown in figure. The portion $BCD$ is frictionless. There are two 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 a small friction and ball $2$ has a negligible friction. For which balls is total mechanical energy conserved?

• A. $1$ and $2$
• B. $1$
• C. $2$
• D. Cannot be predicted

Answer 1

Answer: (A)

$1$ and $2$

Ball 1 has pure rolling form A to B and for renaming part it will have rolling motion so energy will not loss. Whereas in the case of ball 2 there are no friction and no energy loss.
$\therefore$ In both cases total mechanical energy will be conserved.