Topic: Theory of Machines
What is true in respect of the self locking screw jack with square thread? (I) The friction angle is more than the helix angle of the thread. (II) The efficiency of the screw jack should not be more than 50%
- A. Only I
- B. Only II
- C. Both I and II
- D. None of the above
Answer: C. Both I and II
Explanation: For a screw to be self-locking, the friction angle must be greater than or equal to the helix angle (lead angle) of the thread. Consequently, the mathematical maximum efficiency of a self-locking square-threaded screw jack is 50%. Therefore, both statements are true.