Question

9. A solid rectangular block of copper 5 cm by 4 cm by 2 cm

is drawn out to make a cylindrical wire of diameter 2 mm.
Calculate the length of the wire.

Answer 1

length = 1273.2 cm or 12.73 m

Explanation:

Assume no loss.

diameter of wire, d = 2 mm

radius of wire, r = 1 mm = 0.1 cm

Volume of block, V = 5*4*2 = 40 cm^3

cross sectional area of wire, A = pi (r^2) = pi 0.1^2 = 0.01pi cm^2

Length of wire

= V/A

= 40 cm^3 / 0.01pi cm^2

= 4000/pi cm

= 1273.2 cm

= 12.73 m