5 13681.03 Question 2 Requirements • Newtonmeter 0–10 N to 0.1 N × 2 • Pulley to be hung from or clamped to retort stand × 2 • Retort stand, 75 cm tall × 2 • G-clamp × 2 • String • 100 g mass hanger × 2 • 50 g masses × 4 • Sand • Small plastic bag such as a food storage bag • Paperclip • Protractor to 1° Preparation Fill the plastic bag with approximately 120 g of sand. Tie a knot in the top of the bag. Open the paperclip out and hook one end through the knot, leaving the other end to act as a hanger as shown in Fig 2.1. Fig 2.1 Place a 50 g mass on each mass hanger. 6 13681.03 Before the examination Clamp a pulley close to the top of each retort stand ensuring that both pulleys are at the same height. Use the G-clamps to clamp the retort stands to the desk. Use the string and newtonmeters to set up the arrangement shown in Fig 2.2. Tie either end of a string (approx length 6 cm) to the hooks of the newtonmeters. Attach a small loop to the centre of this string. From the other end of each newtonmeter tie a string that will pass over the pulley and attach to a mass hanger with a 50 g mass added. Fig. 2.2 Check that, when the bag of sand is hung from the loop, the bag does not touch the bench and the mass hangers do not hit the pulleys, as shown in Fig. 2.3 Fig. 2.3 7 13681.03 When a spare 50 g mass is added to each hanger, check that the newtonmeters do not hit the pulleys, as shown in Fig. 2.4 Fig 2.4 Action at changeover Remove the two spare 50 g masses and the bag of sand and set them close to the apparatus. Set the protractor close to the apparatus so returning the apparatus to its original arrangement (as in Fig 2.2).