16.If d is the normal diameter of a bolt in mm, then the initial tension in kg in a bolt used for making a fluid tight joint as for steam engine cover joint is calculated by the relation

17.The shearing stresses in the inner face as compared to outer face of the wire in a heavy close coiled spring is

18.Applications in which stresses are encountered in one direction only uses following type of threads

19.If threads on a bolt are left hand, threads on nut will be

20.Which of the following pipe joints would be suitable for pipes carrying steam