ENGINEERING AM1100 MECHANICS
Tutorial V (Friction)
1. A rigid slab of uniform thickness is being hanged by two ropes which are connected to
blocks (see figure 1). The friction coefficients of two surfaces are given in the figure. Consider
the static and kinetic friction coefficients are same. (a) What is maximum weight of the slab (W0)
can be hanged at its horizontal position? When the weight of the slab W > W0 the slab will start
tilting as the left block will start moving. However it will not fall freely unless right block will
also start moving. The slab will have the maximum weight (Wmax) when right block is about to
move. At the condition of impending motion answer the follwing questions.
(b) From geometry write down the relation among 1, 2, and .
(c) At this condition what will be tensile forces in
and
.
(d) For the rigid slab at this position, write down equilibrium equation
Figure 1
2. A cylinder of W weight is supported by two semicircular cylinders. The coefficients of static
friction coefficients between semicircular cylinder and horizontal surface is 0.4 and between the
cylindrical surfaces of the cylinders is 0.3. Determine the maximum distance b (shown in figure)
for which equilibrium is possible.
Figure 2
3. The rod AD is pulled at A and it moves to the left. If the coefficient of the dynamic friction
for the rod at A and B is 0.4, what the minimum value of W2 be to prevent the block from tipping
when =200? With this value of W2 determine the minimum coefficient of static friction between
the block and the supporting plane needed to just prevent the block from sliding.
Figure 3
4. A counterclockwise moment M = 150 Nm is applied to the flywheel. If the coefficient of
friction between the band and the wheel is 0.2, compute the minimum force P necessary to
prevent the wheel from rotating.
Figure 4