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06 homework FONTENOT, BRIAN Due: Feb 25 2008, 4:00 am 4. N 480 N Question 1, chap 7, sect 1. part 1 of 3 10 points Assume you are on a planet similar to Earth where the acceleration of gravity g 10 m/s2 . A plane 50 m in length is inclined at an angle of 16.3 as shown. A block of weight 500 N is placed at the top of the plane and allowed to slide down. 5. N 200 N 6. N 400 N 7. N 120 N 8. N 80 N Question 3, chap 7, sect 1. part 3 of 3 10 points 1 48 m The mass of the block is most nearly 1. m 25 kg 2. m 26 kg 3. m 39 kg 4. m 10 kg 5. m 52 kg 6. m 15 kg 7. m 20 kg 8. m 13 kg 9. m 50 kg Question 2, chap 7, sect 1. part 2 of 3 10 points Calculate the magnitude of the normal force exerted on the block by the plane. 1. N 240 N 2. N 160 N 3. N 360 N 14 m v 50 m 500 N 0.5 16.3 = Calculate the work done on the block by the gravitational force during the 50 m slide down the plane in J. 1. W 1750 J 2. W 3690 J 3. W 7000 J 4. W 10400 J 5. W 1350 J 6. W 650 J 7. W 3750 J 8. W 5850 J 9. W 2400 J Question 4, chap 7, sect 1. part 1 of 3 10 points Sally applies a horizontal force of 706 N with a rope to drag a wooden crate across a floor with a constant speed. The rope tied to the crate is pulled at an angle of 42 relative to the floor. The acceleration of gravity is 9.8 m/s2 . homework 06 FONTENOT, BRIAN Due: Feb 25 2008, 4:00 am Question 9, chap 7, sect 2. part 2 of 2 10 points 42 2 F m 706 N Find the change in kinetic energy of the particle between the same two points. Answer in units of J. Question 10, chap 7, sect 2. part 1 of 2 10 points The force required to stretch a Hooke's-law spring varies from 0 N to 58.8 N as we stretch the spring by moving one end 12.7 cm from its unstressed position. Find the force constant of the spring. Answer in units of N/m. Question 11, chap 7, sect 2. part 2 of 2 10 points Find the work done in stretching the spring. Answer in units of J. Question 12, chap 7, sect 2. part 1 of 1 10 points A force Fx acts on a particle. The force is related to the position of the particle by the formula Fx = (7.9 N/m3 ) x3 . Find the work done by this force on the particle as the particle moves from x = 1.2 m to x = 24 m. Answer in units of J. Question 13, chap 7, sect 3. part 1 of 3 10 points Sally has a mass of 48.8 kg and is moving with a speed of 10.5 m/s. Find Sally's kinetic energy. Answer in units of J. Question 14, chap 7, sect 3. part 2 of 3 10 points Sally's speed changes to 12 m/s. Now what is her kinetic energy? Answer in units of J. Question 15, chap 7, sect 3. How much force is exerted by the rope on the crate? Answer in units of N. Question 5, chap 7, sect 1. part 2 of 3 10 points What work is done by Sally if the crate is moved 65.4 m? Answer in units of J. Question 6, chap 7, sect 1. part 3 of 3 10 points What work is done by the floor through force of friction between the floor and the crate? Answer in units of J. Question 7, chap 7, sect 1. part 1 of 1 10 points A tugboat pulls a ship with a constant net horizontal force of 5.28 103 N and causes the ship to move through a harbor. How much work does the tugboat do on the ship if each moves a distance of 4.29 km ? Answer in units of J. Question 8, chap 7, sect 2. part 1 of 2 10 points A single conservative force acting on a particle varies as F = (-A x + B x2 ) ^ , i where A = 14 N/m and B = 12 N/m2 and x is in meters. Find the change in potential energy as the particle moves from x0 = 3.2 m to x1 = 2.8 m . Answer in units of J. homework 06 FONTENOT, BRIAN Due: Feb 25 2008, 4:00 am part 3 of 3 10 points part 5 of 5 10 points 3 What is the ratio of the first kinetic energy to the second one? 1. v2 v1 v2 2. 1 2 v2 v1 3. v2 v2 4. 2 2 v1 Question 16, chap 7, sect 3. part 1 of 5 10 points A 13.6 kg crate is pulled up a rough incline with an initial speed of 1.6 m/s. The pulling force is 147.0 N parallel to the incline, which makes an angle of 11.1 with the horizontal. The coefficient of kinetic friction is 0.30 and the crate is pulled a distance of 7.6 m. The acceleration of gravity is 9.81 m/s2 . a) Find the work done by Earth's gravity on the crate. Answer in units of J. Question 17, chap 7, sect 3. part 2 of 5 10 points b) Find the work done by the force of friction on the crate. Answer in units of J. Question 18, chap 7, sect 3. part 3 of 5 10 points c) Find the work done by the puller on the crate. Answer in units of J. Question 19, chap 7, sect 3. part 4 of 5 10 points d) Find the change in kinetic energy of the crate. Answer in units of J. Question 20, chap 7, sect 3. e) Find the speed of the crate after it is pulled 7.6 m. Answer in units of m/s. Question 21, chap 7, sect 3. part 1 of 1 10 points Five ramps lead from the ground to the second floor of a workshop, as sketched below. All five ramps have the same height; ramps B, C, D and E have the same length; ramp A is longer than the other four. You need to push a heavy cart up to the second floor and you may choose any one of the five ramps. Assuming no frictional forces act on the cart, which ramp would require you to do the least work? A B C D E 1. Ramp C. 2. Ramp D. 3. Ramp A. 4. Unable to determine without knowing the exact profiles of ramps C, D or E. 5. Ramp E. 6. Same work for the straight ramps A and B; less work for ramps C, D, and E. 7. Ramp B. 8. Same work for ramps B, C, D or E; more work for ramp A. homework 06 FONTENOT, BRIAN Due: Feb 25 2008, 4:00 am 9. Same work for all five ramps. Question 22, chap 7, sect 4. part 1 of 1 10 points A carpenter places a board weighing 23 lb on the edge of the roof 21 ft above the ground. How much potential energy does the board have in relationship to the ground? Answer in units of ft lb. Question 23, chap 7, sect 4. part 1 of 1 10 points Given: G = 6.67259 10-11 N m2 /kg2 A 1200 kg meteor comes in from outer space and impacts on the a moon's surface (this moon is not necessarily the Earth's moon). The mass of this moon is M = 6 1022 kg, and the radius of this moon is R = 1.4 106 m. How much work is done by the Moon's gravitational field? Answer in units of J. Question 24, chap 7, sect 4. part 1 of 3 10 points A mover's dolly is used to deliver a refrigerator up a ramp into a house. The refrigerator has a mass of 145 kg . The ramp is 1.9 m long and rises 0.209 m . The mover pulls the dolly with constant velocity and with a steady force of 486 N up the ramp. The dolly and ramp constitute a machine. The acceleration of gravity is 9.8 m/s2 . What work does the mover do? Answer in units of J. Question 25, chap 7, sect 4. part 2 of 3 10 points What gravitational potential energy is gained by the refrigerator? Answer in units of J. Question 26, chap 7, sect 4. part 3 of 3 10 points What is the efficiency of the machine? Answer in units of percent. Question 27, chap 7, sect 4. part 1 of 3 10 points 4 A 2.17 kg ball is attached to a ceiling by a 2.05 m long string. The height of the room is 5.67 m . The acceleration of gravity is 9.8 m/s2 . What is the gravitational potential energy associated with the ball relative to the ceiling? Answer in units of J. Question 28, chap 7, sect 4. part 2 of 3 10 points What is its gravitational potential energy relative to the floor? Answer in units of J. Question 29, chap 7, sect 4. part 3 of 3 10 points What is its gravitational potential energy relative to a point at the same elevation as the ball? Answer in units of J. ... View Full Document

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