6 11969.03 Question 3 Requirements • Single layer DVD or CD ROM × 4 • 10 g mass (diameter approx. 33 mm) × 2 • 20 g mass (diameter approx. 33 mm) × 2 • Stopclock • Double sided foam sticky pads, e.g. Sellotape sticky fixers × 6 • Labels/marker suitable for writing on DVD Preparation Use the double sided foam sticky pads to stick one of the 10 g masses to the DVD/CD as shown in Fig 3.1. Stick another 10 g mass directly on top of the fi rst and then a second DVD/CD on top. Label this ‘System 1: m = 25 g’. The arrangement should sit as shown in Fig 3.1. Repeat with the other 2 DVD/CDs, this time with two 20 g masses stuck in between. Label this ‘System 2: m = 45 g’. Draw an arrow pointing vertically downwards when the DVD/CD sits on the bench as shown in Fig 3.2. When displaced slightly the system should oscillate in excess of 10 oscillations. The period of oscillation of System 2 should be less than System 1. Side view double sided foam sticky pads 10g masses desk DVD/CDs Front view Fig. 3.1 Fig. 3.2 Before the examination Set system 1 upright on the desk. Leave the other on the desk close by with the stopclock. Action at changeover Return the apparatus to the original arrangement.