Question

Period Date Name 39 Solitary Seesaw Purpose To identify the forces, lever arms, and torques for a system in rotational 2 knife-edge lever clamps set of slotted masses 2 mass hangers fulcrum string or masking tape Gravity pulls on every part of an object. The average position of these pulls (the weight) is the center of gavity (CG) of the object. The sum of all these pulls is the weight of the object. The entire weight of the object is effectively concentrated at its CG. The CG of a uniform meterstick is at the geometric center the 50-cm mark. In this exper pute the mass of an unknown mass using the balanced torque equation Fd Fody. Then you will simulate a "solitary" seesaw by balancing the iment you will use a meterstick as a seesaw and com- Step 1: Balance the meterstick horizontally with nothing hanging from it. Record the position of the CG of the meterstick. position of the meterstick CG- 50 cm Chapter 11 Rotational Equilibeium 145 Using a string or weight hanger, attach a unknown mass such as a rock on one side of the fulcrum at the 90-cm mark as shown in Figure A Place a known mass on the other side to balance the meterstick Record the known mass and its position Unknown Mass Known Mass at 90-cm Mark Step 2 Measure the distances from the fulcrum to each mass. di distance from fulcrum to known mass d2 distance from fulcrum to unknown mass- These two distances are known as lever arms. The lever arm is the (per- pendicular) distance from the fulcrum to the imaginary line that passes through the force (called the line ofaction) of the force. Write down the equation for the balanced torques with the known values. Calculate the unknown mass equation: Step 3: Measure the unknown mass using a balance or spring scale 1. How does your calculated value compare with your measured value of the unknown mass? Step 4: Place the fulcrum exactly on the 85-cm mark. Balance the meter- stick using a single known mass that you hang between the 90-cm and 95-cm mark as in Figure B. Record the mass used and its position. Fig. B known mass- distance Laboratory Manual Actlivity 39) Name Period Date Step 5: Identify the lever arms, forces and resulting torques for this soli- tary seesaw. This is not as easy as it was for Step 2. In that case, the lever arms and forces were dlearly visible and easy to discern. There's clearly a force on the right side of the fulcrum causing a clockwise torque But what about the balancing torque on the left side of the fulcrum? Remember, since the meterstick is in rotational equilibrium, the sum of the tonques is zero, so there must be a counter-clockwise torque balanc- ing it. Clearly identify the forces and the distance the forces are from the fulcrum for each side. known mass distance unknown mass8 distance» cm Analysis 2. Use Fid Fd to calculate the location of the CG for the meterstick in the solitary seesaw. How does it compare with your results in Step I? Compute the percent error 3. What fraction of the mass of the meterstick is on the right side of the fulcrum? 24. What fraction of the mass of the meterstick is on the left side of the fulcrum? 5. How much of the mass of an object behaves as if it is located at the CG

Answer 1

mn dレ 9) Mg finaf knawin nnun maり«M.ma/y