The following four wires of length $L$ and radius $r$ are made of the same material. Which of these will have the largest extension, when the same tension is applied?

The upper end of a wire of diameter $$24 \mathrm{~mm}$$ and length $$1 \mathrm{~m}$$ is damped and its other end is twisted through an angle is $$30^{\circ}$$. The angle of shear is

The elastic limit of $$1 \mathrm{~kg}$$ mass is $$3.5 \times 10^{10} \mathrm{~N} / \mathrm{m}^2$$. Find the maximum load that can be applied to a brass wire of a $$1 \mathrm{~mm}$$ diameter without exceeding the elastic unit.

A wire of cross-section $$A$$ is stretched horizontally between two clamps located $$2 l$$ metre apart. A weight $$w \mathrm{~kg}$$ is suspended from the mid-point of the wire. If the mid-point sags vertically through a distance $$x<1$$, the strain produced is