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Den Hartog’s Mechanics

A web-based solutions manual for statics and dynamics

Problem 43

As the roller is starting to go up over the plank, the contact force between the roller and the ground goes to zero. The free-body diagram for this condition is shown below.

To determine P, we take moments about A, the contact point between the plank and the roller.

\sum M_A = P \cdot 8 - 300 \cdot \sqrt{9^2 - 8^2} = 0

The solution is P = 155 lbs, which, except for roundoff, matches the answer in the back of the book.

Problem 44Problem 42

Last modified: January 22, 2009 at 8:32 PM.