# Ch5 HW3 - Ch5 HW3...

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BRANDON JARROTT FELDKAMP PHYS 2211, section M, Fall 2008 Instructor: Jennifer Curtis Web Assign Current Score: 25 out of 26 Due: Friday, October 3, 2008 09:00 AM EDT Description The Energy Principle: Change of identity; Work done by non-constant forces Instructions Reading: Sections 5.5-5.7 The due date for this assignment is past. Your work can be viewed below, but no changes can be made. 1. [MI2 05.X.22] 2/2 points You push a box out of a carpeted room and along a hallway with a waxed linoleum floor. While pushing the crate 2 m out of the room you exert a force of 26 N; while pushing it 6 m along the hallway you exert a force of 12 N. To bring it to a stop you exert a force of 6 N through a distance of 1.2 m, opposite to the motion. How much work do you do in all? 116.8 117 J Solution or Explanation W = 1 · 1 + 2 · 2 + 3 · 3 Be careful about signs: 3 · 3 = F x 3 x 3 is negative , since the force has a negative x component. 2. [MI2e 5.P.61] 4/4 points A crate with a mass of 50 kg glides through a space station with a speed of 3.5 m/s. An astronaut speeds it up by pushing on it from behind with a force of 220 N, continually pushing with this force through a distance of 5 m. The astronaut moves around to the front of the crate and slows the crate down by pushing backwards with a force of 210 N, backing up through a distance of 3 m. What is the total amount of work done by the astronaut in these two maneuvers? W = 470 470 J After these two maneuvers, what is the speed of the crate? v

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Ch5 HW3 - Ch5 HW3...

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