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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 θ . mg P F θ R Determine the torque equation about the point P . 1. Rmg = (1 + sin θ ) RF correct 2. Rmg = (2- sin θ ) RF 3. Rmg = (1 + cos θ ) RF 4. Rmg = RF 5. Rmg = (2- cos θ ) RF 6. Rmg = 2 cos θ RF 7. Rmg = 2 sin θ RF Explanation: mg P F θ A θ About P, the clockwise torque is, τ cw = AP × F , where AP = R ( 1 + sin θ ) and the clockwise torque, τ ccw = Rmg . Therefore Rmg = (1 + sin θ ) 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 θ with respect to the vertical wall. m R A B θ 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 θ 2. mg = F A tan θ correct 3. mg = F A sin θ 4. mg = 1 2 F A sin θ 5. mg = 2 F A tan θ 6. mg = 2 F A cos θ 7. mg = 1 2 F A cos θ 8. mg = F A cos θ 9. mg = 1 2 F A tan θ Explanation: The free body diagram is F A F B F B mg θ F A mg θ The three forces form a right triangle with F B as the hypotenuse, so tan θ = mg F A mg =...

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