This was a popular question and candidates performed very well in it. However, some candidates did not convert L the unit of mass (grammes) into newton. Though some spring balances in the market are calibrated in grammes, so in response to the question, some candidates presented their answers in grammes and it was accommodated by the marking scheme. It was also discovered that some candidates recorded their first set of spring balance readings in air correctly but got the readings in liquid t out of trend. The weights measured (ii air and liquid L, were not probably recorded/tabulated immediately after measurement hence were muddled up.
b (i) This was well stated by most candidates
(ii) The numerical part was not well tackled by most candidates.
The expected answers are:
(i) Five values of weight of object in air W1 recorded in gm/IN
(ii)Five values of weight of object in wafer (W2) in gm/N recorded and in trend (Trend: W2 < W1)
(iii)Five values of weight of object in liquid L (W3) to 1 d. p and in trend (Trend W1 > W3 >W2)
(iv)Five values of U =(W1 – W2) correctly evaluated
(v)Five values of V (W1  W3) correctly evaluated
(vi)Composite table showing W1, W2, w3, U and V
Candidates are also expected to: (i)Plot five points on graph (ii) Distinguish between the axes (iii)Chose reasonable scales (iv)Draw line of best fit (v)Determine the slope of the graph
State any two of the following precautions.
 Avoided parallax error in reading spring balance
 Avoided noted zero error of spring balance
 Avoided splashing of liquid
 Avoided object touching bottom or sides of beaker
 Cleaned mass before dipping it into liquid
 Repeated readings shown on the table.
(b) (i) Archimedes’ Principle  states that when a body is wholly or partially
immersed in a fluid (liquid) it experiences an upthrust which is equal to the weight of the fluid(liquid) displaced.
(ii) (Weight of Kerosene displaced) * ( volume of object) x (Density of Kerosene) x£
Mass of object x density of kerosene x g Density of object
20 x 10^3 x 8.0 x 10^3 x 10 8x 10^3
0.02N = Upthrust of kerosene on object
Weight of object in air = Mass x g
20 x 10'3 x 10 = 0.2N
Tension in the spring  (weight of object  Upthrust in air) = 0.2 0.02
Reading of the balance = 0.18N
