In this experiment you will determine the speed of a wave on the surface of water. You are provided with: • a plate filled with water • a dropping pipette • a stop-watch • a 30 cm ruler • a small beaker of water • paper towels to mop up any spillages.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

1. [1] (a) Apply pressure / squeeze the bulb / soft end (of the pipette to push air out);
2. [1] (a) put (open end) into water and remove pressure / release the end ;
3. [1] (a) until water is level with 1 ml/cm³ mark
4. [1] (b)(i) at least two measurements of time seen, to 0.1 s or better;
5. [1] (b)(i) times averaged and average time, t, in the range from 0.75 to 1.25 s ;
6. [1] (b)(ii) Distance travelled = diameter of plate recorded or = 2 x radius of plate;
7. [1] (b)(ii) calculation of speed using their values (cm/s);
8. [2] (c)(i) Any two from :: difficult to place droplet in centre of plate, difficult to hold ruler steady, parallax error when reading both ends of rule, the speed of the wave is too fast, reaction time affects the the time measurement / times are very small, the water / plate is not of uniform depth / is difficult to measure using the ruler
9. [1] (c)(ii) Any one from ; mark the centre of the plate, clamp the rule / ruler in place / rest ruler on the plate, use a larger plate to reduce effect of error due to reaction time, ensure eye is vertically above scale in rule (to avoid parallax), how to use technology (e.g. video) to improve timing, use a plate with uniform depth / use vernier calipers to measure the depth.