Engineering Statics

E-12


The coefficient of friction 0.40 for static friction and 0.30 for dynamic friction between all surfaces. Determine the smallest force, P, required to start the 30 kg block moving if cables AB (a) is attached as shwon, (b) is removed.

The FBD of the upper and lower blocks are shown and their 
weights are calculated by multiplying their mass by 
9.8 m/s/s, the acceleration due to gravity.
The force equation in the y-direction is written for the 
upper block.
The normal force between the two blocks is found.
The force equation in the y-direction is written for the 
lower block.
The normal force between the lower block and the floor 
is found.