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Names: PURPOSE In this lab you will examine a system that is in mechanical equilibrium. Your job in each case is to measure the distances, angles and forces relevant to the system and use that data to find unknown masses of objects in the system. You are not allowed to disassemble the systems! MATERIALS AND EQUIPMENT Pre-built Equilibrium systems Protractor Lab: Equilibrium PROCEDURE Visit one of the two stations where a system in equilibrium have been set up for you. For one of the systems, you need to collect enough data to set up equilibrium equations and calculate the two unknown masses (mass of the horizontal rod and the hanging mass). You may not disassemble or alter the systems in any way. You are allowed to measure angles using protractors (if applicable) and distances using rulers. The forces are already measured for you though the use of the scales, where the reading can be recorded in newtons. For one of the systems given, follow these steps: 1. Choose one of the two systems available. The initial setup is already drawn for you on the next page (or you can draw your own), only to make sure that everybody refers to all the forces and distances in the same manner. You will have to draw a complete and labeled extended FBD for each. Use of graph paper is highly encouraged. Use a ruler to make nice straight lines. You will be graded on neatness. Lad Timi 2. Using your drawing from #1, draw an extended FBD, labeling all the forces and distances with descriptive labels (for example, F f f 8, etc.). Make sure to draw each force vector at the correct location on the object it is acting upon, and in the correct direction. Remember that force of gravity acts at the center-of- mass of an object. 3. Fill in a table of measurements that you had to make in order to be able to solve the system. Make sure that the values of all the measurements agree with the labels on the diagrams. Table is already prepared for you, you just need to fill in the values, but feel free to add other measurements to these as necessary. fr 12 Ruler/meter stick Level (provided with the system) Table of measured values: Distances (in meters) 95M 225 012 -41 Fri Fre Forces (in newtons) 20 0.5 Instructor initials 4. Set up the three equilibrium equations. Hint: For the torque equations, choose the pivot point so that you eliminate as many forces as possible. 5. Simplify the equations as much as possible algebraically to be able to quickly plug in values once experimental measurements are made. You will lose points if you solve the entire system numerically.
4. Set up the three equilibrium equations. Hint: For the torque equations, choose the pivot point so that you eliminate as many forces as possible. 5. Simplify the equations as much as possible algebraically to be able to quickly plug in values once experimental measurements are made. You will lose points if you solve the entire system numerically. System drawing Ful Tal mm m₂ Scale 1-Fr Lov m₂ m CM m₁ m₂ M Scale 2-Fr 6. Calculate the two unknown masses, and record your results in the table below. Experimental results 8 Note: if you got a negative value for the mass, carefully describe experimental and algebraic errors that could've contributed to this error. 7. When everyone has had a chance to make the measurements, your instructor will disassemble the systems, and will give you the actual masses. Record these masses in the table below, and calculate % error for both. Show your calculations in the space below. Experimental results % error Instructor initials, 8. For the lab report, staple together this sheet with results, the complete system drawings with FBD, and all the equations and calculations. There is no formal lab write-up for this lab, but you will be graded on neatness, clarity, readability, completeness, and correctness. Make sure to obtain instructor initials-they are worth double the usual amount of points. Instructor initials