Crates A and B are connected by cable CD and rest upon a wooden plank as shown above. Crate A weighs 225 lbs and crate B weighs 175 lbs. An additional force P can be applied to crate B which is parallel to the plank. The coefficient of static friction between crate and plank is μs = 0.25 for both crates. The wooden plank is able to be raised to any angle θ. Neglect the weight of the cable. A. If no external forces are applied ( P = 0 ) and the plank is gradually raised, which crate starts slipping first? B. If no external forces are applied ( P = 0 ) and the plank is gradually raised, at what angle does the crate chosen from part A start slipping? C. If the plank is raised to θ = 20° what is the minimum external force P that can be applied in order to prevent the crates from slipping?
Crates A and B are connected by cable CD and rest upon a wooden plank as shown above. Crate A weighs 225 lbs and crate B weighs 175 lbs. An additional force P can be applied to crate B which is parallel to the plank.
The coefficient of static friction between crate and plank is μs = 0.25 for both crates.
The wooden plank is able to be raised to any angle θ.
Neglect the weight of the cable.
A. If no external forces are applied ( P = 0 ) and the plank is gradually raised, which crate starts slipping first?
B. If no external forces are applied ( P = 0 ) and the plank is gradually raised, at what angle does the crate chosen from part A start slipping?
C. If the plank is raised to θ = 20° what is the minimum external force P that can be applied in order to prevent the crates from slipping?
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