A concrete highway is built of slabs 12 m long (at 15◦ C). How wide should the expansion cracks between the slabs be (at 15◦ C) to prevent buckling of the range of temperature is -30◦ C to +50◦ C?

Asteel wire of 2 mm diameter is fixed between two points located 2 m apart. the tensile force in the wire is 250n, if its density of steel is given by 7830 kg/m3 the fundamental frequency of vibration hz? ?