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Unformatted text preview: homework 19 RAHMAN, TARIQUE Due: Apr 11 2008, 3:00 am 1 Question 1, chap 14, sect 1. part 1 of 1 10 points Consider the wheel-and-axle system shown below. a b m 1 m 2 Which of the following expresses the con- dition required for the system to be in static equilibrium? 1. am 2 = bm 1 2. am 1 = bm 2 correct 3. a 2 m 1 = b 2 m 2 4. b 2 m 1 = a 2 m 2 5. m 1 = m 2 Explanation: In equilibrium, the total torque is zero, which gives am 1 = bm 2 . Question 2, chap 14, sect 1. part 1 of 1 10 points Consider a solid sphere of radius R and mass m held against a wall by a string being pulled at an angle . mg P F R Determine the torque equation about the point P . 1. Rmg = (1 + sin ) RF correct 2. Rmg = (2- sin ) RF 3. Rmg = (1 + cos ) RF 4. Rmg = RF 5. Rmg = (2- cos ) RF 6. Rmg = 2 cos RF 7. Rmg = 2 sin RF Explanation: mg P F A About P, the clockwise torque is, cw = AP F , where AP = R ( 1 + sin ) and the clockwise torque, ccw = Rmg . Therefore Rmg = (1 + sin ) RF . homework 19 RAHMAN, TARIQUE Due: Apr 11 2008, 3:00 am 2 Question 3, chap 14, sect 1. part 1 of 1 10 points Consider a solid sphere of radius R and mass m placed in a wedge, where one wall is vertical and the other wall has an angle with respect to the vertical wall. m R A B Assuming that the walls are smooth, which expression is appropriate if you consider a free body diagram for the ball which involves F A and F B , the forces acting on the contact points A and B, respectively, and the weight mg ? 1. mg = 2 F A sin 2. mg = F A tan correct 3. mg = F A sin 4. mg = 1 2 F A sin 5. mg = 2 F A tan 6. mg = 2 F A cos 7. mg = 1 2 F A cos 8. mg = F A cos 9. mg = 1 2 F A tan Explanation: The free body diagram is F A F B F B mg F A mg The three forces form a right triangle with F B as the hypotenuse, so tan = mg F A mg =...
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