Question

A small Iab scale has a rigid L-shaped frame ABC consisting of a hori arm AB (length b 280 mm) and a vertical arm BC (length c 250 pivoted at point B, as shown in Fig. 2-7a. The pivot is attached to th frame BCD, which stands on a laboratory pointer at C is controlled by a spring (stiffness 750 N/m the attached to a threaded rod. The position of the threaded rod is by turning the knurled nut The pitch of the threads (that is, the distance from one thread to t next) is p 1 move the rod by that same amount. Initially, when there is no hanger, the nut is turned until the pointer at the end of arm BC is direcn over the reference mark on the outer frame bench. The position of the that is s adjusted 1.6 mm, which means that one full revolution of the nut w on the weight on tha rect (a) If a weight W- 9 N is placed on the hanger at A, how many revolutions of the nut are required to bring the pointer back to the mark? (Deformations of the metal parts of the device may be disregarded because they are negligible compared to the change in length of the spring ) (b) If a rotational spring of stiffness k, kb'/4 is added at B, how many revolutions of the nut are now required? (The rotational spring provides resisting moment k, (N-m/radian) for unit angular rotations of ABC) Hange Frae Knurled nur Spring R Threaded rod

Answer 1

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