Question
(a) A student places 8 similar coins in a pile, as shown in Fig. 1.1.
The height of the pile of coins is 2.4 cm.
Calculate the average thickness of one coin.
average thickness = ………………………………………….. cm
(b) Fig. 1.2 shows the pile of coins, a measuring cylinder and a beaker containing some water.
Describe how the student can measure the volume of one of the coins using the set-up shown in Fig. 1.2.
Answer/Explanation
Answer:
(a) (average thickness =) 2.4 ÷ 8
(average thickness =) 0.3 (cm)
Question
(a) Define density.
(b) The density of aluminium is 2.70 \(g/cm^3\). The thickness of a rectangular sheet of aluminium foil varies, but is much less than 1 mm.
A student wishes to find the average thickness. She obtains the following measurements.
mass of sheet = 60.7 g
length of sheet = 50.0 cm
width of sheet = 30.0 cm
Calculate the student’s values for
(i) the volume of the sheet,
volume = ……………………………………..
(ii) the average thickness of the sheet.
thickness =
(c) Another student, provided with a means of cutting the sheet, decides to find its average thickness using a single measuring instrument. Assume the surfaces of the sheet are perfectly smooth.
(i) Name a measuring instrument she could use.
(ii) Describe the procedure she should follow to obtain an accurate value of the average thickness of the sheet.
Details of how to read the instrument are not required.
Answer/Explanation
Answer:
(a) (density =) mass/volume OR mass per unit volume OR m/V with symbols explained
(b) (i) (vol =) mass/density OR 60.7/2.70 = 22.48 \(cm^3\) to 2 or more sig. figs
(ii) V = A × (average) thickness OR thickness = V/A OR 22.48 / (50 × 30)0.01499 cm to 2 or more sig. figs. e.c.f.
(c) (i) micrometer/screw gauge / (vernier/digital) callipers
(ii) check zero of device used / cut sheet into several pieces / detail of how to use\ device / fold sheet measure thickness of sheet in different places
OR measure thickness of several pieces together calculate/obtain average thickness OR divide answer by number of measurements/
pieces/places