Engr Help

Example involving Friction

A uniform rectangular block of weight, W, is initially at rest on a horizontal plane as shown

below. A variable force, P, acts on the block at point E. The width of the block is b and its

height is h. Find the magnitude of force, P, that causes motion of the block to impend. The

following data applies:

μ= 1/3, b = 3 ft, h = 4 ft, W = 80 lb, sin θ = 3/5

Apply the following strategy.

Construct a FBD of the block.

Determine the different possibilities for impending motion.

In this example impending motion either involves sliding or tipping.

Write the equations of equilibrium for the block.

Check these equations to determine the unknowns.

Investigate conditions for impending sliding and impending tipping.

Check results for each case to determine which motion first impends.