Newton_s Laws Problems

# 7 a worker drags a crate across a factory floor by

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In the above problem, if the string is cut, with what acceleration will the block move? 7. A worker drags a crate across a factory floor by pulling on a rope tied to the crate. (See figure below.) The worker pulls on the rope, which is inclined at 38 ˚ to the horizontal, and the floor exerts a horizontal force of 125 N that opposes the motion (friction). Calculate the force that the worker exerts on the rope if the crate is moving at constant velocity. m frictionless θ 125 N F 38 ˚

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Ms. Todd’s Honors Physics Name_______________________________ More Newton’s Law Problems 1. A 90 kg firefighter slides down a vertical pole with an acceleration of 3 m/s 2 , directed downward. What are the magnitudes and directions of the vertical forces (a) exerted by the pole on the firefighter and (b) exerted by the firefighter on the pole? 2. Two blocks are in contact on a frictionless table. A horizontal force is applied to one block, as shown below. (a) If m 1 = 2.3 kg, m 2 = 1.2 kg, and F = 3.2 N, find the force of contact between the two blocks. (b) Show that if the same force F is applied to m 2 rather than to m 1 , the force of contact between the blocks is 2.1 N, which is not the same value derived in (a). Explain the difference. 3. An 80 kg man jumps down to a concrete patio from a window ledge only 0.50 m above the ground. He neglects to bend his knees on landing, so that his motion is arrested in a distance of 2.0 cm. (a) What is the average acceleration of the man from the time his feet first touch the patio to the time he is brought fully to rest? (b) With what force does this jump jar his bone structure? (c) What force does the man exert on the patio? m 1 m 2 F m 1 m 2 F (a) (b)
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