Q1. If the coefficient of static friction between all the surfaces of contact is µs, determine the
force P that must be applied to the wedge in order to lift the block having a weight W.
Fig. 1
Ans:
Q2. Determine the reversed horizontal force – P needed to pull out wedge A. The coefficient of
static friction between A and C and between B and D is µs = 0.2, and between A and B µs/ = 0.1.
Neglect the weight of each wedge.
Fig. 2
Ans: 106 lb
Q3. The column is used to support the upper floor. If a force F = 80 N is applied perpendicular to
the handle to tighten the screw, determine the compressive force in the column. The square
threaded screw on the jack has a coefficient of static friction µs = 0.4, and mean diameter of 25
mm, and a lead of 3 mm.
Fig. 3
Ans: 7.19 kN.
Q4. If couple forces of F = 35 N are applied to the handle of the machinist’s vise, determine the
compressive force developed in the block. Neglect friction at the bearing A. The guide at B is
smooth. The single square-threaded screw has a mean radius of 6 mm and a lead of 8 mm, and
the coefficient of static friction is µs = 0.27
Fig. 4
Ans: 2.85 kN.