(Q3).A copper rod of diameter 1 cm. and length 8 cm; is drawn into a wire of length 18 m of uniform thickness. Find the thickness of the wire.

Answer:

Volume of the copper rod (cylinder)

= πr2h

=
×
×
×
=
m2

If V is the radius of the wire, then its volume = πr2h

∴ The volume of rod is equal to the volume of the wire. We have

 × =
cm3
r2 =
×
×

[∵ = × cm]

r2=
r =
cm = cm

∴ Thickness = d = × ≃ cm.