Determine the required number of active coils and permissable deflection in a helical spring made of 1.6 mm diameter steel wire, assuming a spring index of 6 and allowable stress of 345 mpa in shear. the spring rate is to be 1.75 n/mm.

Water at the rate of 1 kg/s is forced through a tube with a 2.5 cm inner diameter. the inlet water temperature is 15°c, and the outlet water temperature is 50°c. the tube wall temperature is 14°c higher than the local water temperature all along the length of the tube. what is the length of the tube?