Question
Detach the two strings from the bar ABCD to check the zero reading of the spring scale. Without any counterweight, flat circular indicator should be on the zero line. Adjust the top nut if the spring scale is not properly zeroed. As shown in figure 2, attach string 1 to the eye bolt at the centre of gravity (e.g.) and string 2 to the eye bolt at D. To level the bar, put the turnbuckle in the appropriate hole then adjust the turnbuckle for fine tuning. With a square speed and a line level, check that bar ABCD lies along y-axis. This will be known as Case A. Use a meter stick to measure x, y and z components for both string 1 and string 2. Record the results in Data Table 1. Also read the tensions in two strings and record these values as T1 (N) and T2 (N) in Data Table 1. To determine the translational and rotational motion of a body as a whole, we can assume that entire weight of the body (which is the sum of the weights of all its parts) acts at one point: the center of gravity (e.g.) The weight of the bar and (e.g.) have been marked on the bar. Measure the length from the ball and socket joint to e.g. Record this value in Data Table 1. Reattach string 1 to the eye bolt at B and string 2 to C as shown in figure 3- This will be known as Case B. Repeat steps 1) to 3) and record your data in Data Table 2. Figure 3: Rigid body equilibrium for case B Data Table 1: Data for Rigid Body Equilibrium, case A (data is provided) Data Table 2: Data for Rigid Body Equilibrium, case B (data is provided) For both case A and case B, use all the data provided except for the tension measurements to answer the following questions. What are the forces acting on the bar? Express T1, Ta, and W in Cartesian vector form. What are the equilibrium equations of forces? What are the equilibrium equations of moments? Determine T1 and T2. Compare T1 and T2 to the (provided) readings from spring scales and calculate the percentage difference and record them on the Calculations Table. Calculate Ax, Ay, and Az, the reactions at ball and socket joint A.
Explanation / Answer
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