This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: homework 12 YOO, HEE Due: Feb 18 2008, 4:00 am 1 Question 1, chap 6, sect 1. part 1 of 1 10 points There is friction between the block and the table. The suspended 4 kg mass on the left is moving up, the 3 kg mass slides to the right on the table, and the suspended mass 9 kg on the right is moving down. The acceleration of gravity is 9 . 8 m / s 2 . 4 kg 3 kg 9 kg = 0 . 17 What is the magnitude of the acceleration of the system? Correct answer: 2 . 75013 m / s 2 (tolerance 1 %). Explanation: m 1 m 2 m 3 a Let : m 1 = 4 kg , m 2 = 3 kg , m 3 = 9 kg , and = 0 . 17 . Basic Concepts: The acceleration a of each mass is the same, but the tensions in the two strings will be different. F net = ma negationslash = 0 Solution: Let T 1 be the tension in the left string and T 2 be the tension in the right string. Consider the free body diagrams for each mass T 1 m 1 g a T 2 m 3 g a T 1 T 2 N N a m 2 g For the mass m 1 , T 1 acts up and the weight m 1 g acts down, with the acceleration a di rected upward, so F net 1 = m 1 a = T 1 m 1 g . (1) For the mass on the table, a is directed to the right, T 2 acts to the right, T 1 acts to the left, and the motion is to the right so that the frictional force m 2 g acts to the left and F net 2 = m 2 a = T 2 T 1 m 2 g . (2) For the mass m 3 , T 2 acts up and the weight m 3 g acts down, with the acceleration a di rected downward, so F net 3 = m 3 a = m 3 g T 2 . (3) Adding these equations yields ( m 1 + m 2 + m 3 ) a = m 3 g m 2 g m 1 g a = m 3 m 2 m 1 m 1 + m 2 + m 3 g = 9 kg (0 . 17) (3 kg) 4 kg 4 kg + 3 kg + 9 kg (9 . 8 m / s 2 ) = 2 . 75013 m / s 2 . Question 2, chap 6, sect 1. part 1 of 3 10 points The suspended 2 . 3 kg mass on the right is moving up, the 1 . 3 kg mass slides down the ramp, and the suspended 8 . 6 kg mass on the left is moving down. The coefficient of friction between the block and the ramp is 0 . 2 . homework 12 YOO, HEE Due: Feb 18 2008, 4:00 am 2 The acceleration of gravity is 9 . 8 m / s 2 . The pulleys are massless and frictionless. 1 . 3 k g = . 2 27 8 . 6 kg 2 . 3 kg What is the acceleration of the three block system? Correct answer: 5 . 34865 m / s 2 (tolerance 1 %). Explanation: Let : m 1 = 2 . 3 kg , m 2 = 1 . 3 kg , m 3 = 8 . 6 kg , and = 27 . Basic Concept: F net = ma negationslash = 0 Solution: The acceleration a of each mass is the same, but the tensions in the two strings will be different. Let T 1 be the tension in the right string and T 3 the tension in the left string. Consider the free body diagrams for each mass T 3 m 3 g a T 1 m 1 g a T 3 T 1 N N a m 2 g For the mass m 1 , T 1 acts up and the weight m 1 g acts down, with the acceleration a di rected upward F net 1 = m 1 a = T 1 m 1 g (1) For the mass on the table, the parallel compo nent of its weight is mg sin and the perpen dicular component of its weight is mg cos ....
View Full
Document
 Spring '08
 Turner
 Friction, Mass, Work

Click to edit the document details