a copper wire of diameter 6mm is evenly wrapped on a cylinder of length 15cm and diameter 49cm to cover its whole surface . find the length and volume of the wire. if the specific gravity of copper be 9kg per cu cm , find the weight of the wire.

Diameter of copper wire = 6 mm i.e. its radius = 3 mm
Length of cylinder = 15 cm = 150 mm
Diameter of cylinder = 49 cm = 490 mm

Number of turns of copper wire = $\frac{150}{6}=25$
Length of one turn = $2\mathrm{\pi }\left(\frac{490}{2}\right)=490\times \frac{22}{7}=1540 \mathrm{mm}$
So total length of copper wire = $25\times 1540 mm=38500mm$
Therefore volume of copper wire = $\mathrm{\pi }\times {\left(3\right)}^2\times 38500 {\mathrm{mm}}^3=1089000 {\mathrm{mm}}^3$

Volume ( in cubic centimetres ) = 1089 $c{m}^3$
Specific gravity of wire = $9kg/c{m}^3$
So weight of wire = $\left(1089\times 9\right)kg=9801kg$