In a vernier callipers, $(N+1)$ divisions of vernier scale coincide with $N$ divisions of main scale. If $1 \mathrm{MSD}$ represents $0.1 \mathrm{~mm}$, the vernier constant (in $\mathrm{cm}$ ) is:

Using screw gauge of pitch $0.1$ $cm$ and $50$ divisions on its circular scale, the thickness of an object is measured. It should correctly be recorded as 

A screw gauge of pitch $0.5\,mm$ is used to measure the diameter of uniform wire of length $6.8\,cm$, the main scale reading is $1.5\,mm$ and circular scale reading is $7$. The calculated curved surface area of wire to appropriate significant figures is $……cm^2$ . [Screw gauge has $50$ divisions on the circular scale]

There are $100$ divisions on the circular scale of a screw gauge of pitch $1 \mathrm{~mm}$. With no measuring quantity in between the jaws, the zero of the circular scale lies $5$ divisions below the reference line. The diameter of a wire is then measured using this screw gauge. It is found the $4$ linear scale divisions are clearly visible while $60$ divisions on circular scale coincide with the reference line. The diameter of the wire is :

When the gap is closed without placing any object in the screw gauge whose least count is $0.005\ mm$, the $5^{th}$ division on its circular scale with the reference line on main scale, and when a small sphere is placed reading on main scale advances by $4$ divisions, whereas circular scale reading advances by five times to the corresponding reading when no object was placed. There are $200$ divisions on the circular scale. The radius of the sphere is ………. $mm$