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A moving company uses the pulley system in figure to lift heavy crates up a ramp. The ramp is coated with rollers that make the crate's motion essentially frictionless. A worker piles cinder blocks onto the plate until the plate moves down, pulling the crate up the ramp. Each cinder block has mass 10kg. The plate has mass 5kg. The rope is nearly massless, and the pulley is essentially frictionless. The ramp makes a 30° angle with the ground. the crate has mass 100kg.Let W1 denote the combined weight of the plate and the cinder blocks piled on the plate. Let T denote the tension in the rope. And let W2 denote the crate's weight.What is the smallest number of cinder blocks that need to be placed on the plate in order to lift the crate up the ramp? (A) 3 (B) 5 (C) 7 (D) 10 |
| Answer» The correct answer is (B) 5. | |