Using the spring balance provided, determine the weight of object of mass M = 5.0g. Record this weight as \(W_1\).
Determine the weight of the object when completely immersed in water contained in a beaker as shown in the diagram. Record the weight as \(W_2\)
Determine the weight of the object when it is completely immersed in the liquid labelled 'L'. Record the weight as \(W_3\). Evaluate, u = (\(W_1\) -\(W_3\)) and v = (\(W_1\) - \(W_3\)).
Repeat the procedure with the objects of masses M = 10, 15, 20, and 25g. In each case, evaluate u = (\(W_1\) - \(W_3\)) and v = (\(W_1\) - \(W_3\)) on the vertical axis against u = (\(W_1\) - \(W_2\) on the horizontal axis.
Determine the slope, s, of the graph. (vii) State two precautions taken to ensure accurate results.
(b)i. A piece of brass of mass 20.0g is hung on a spring balance from a rigid support and completely immersed in kerosine of density 8.0 x 10\(^{2}\)kg m\(^{-3}\). Determine the reading on the spring balance. [g= 10ms\(^{-2}\)], density of brass = 8.0 x 10\(^{3}\) kg m\(^{-3}\) J
ii. State Archimede's principle and the law of floatation.
Verified Correct Answer: .
Physical Principles & Numerical Solution
M(g)
\(W_1\)(g)
\(W_2\)(g)
\(W_3\)(g)
U=(\(W_1\) - \(W_2\))g
V=(\(W_1\)-\(W_3\))g
5.0
5.00
4.20
4.70
0.80
0.80
10.0
10.00
7.90
8.60
2.10
1.40
15.0
15.00
12.75
13.50
2.25
1.50
20.0
20.00
17.10
16.40
2.90
3.60
25.0
25.00
22.10
21.40
2.90
3.60
Slope = \(\frac{y_{2}-y_{1}}{x_{2}-x_{1}} = \frac{2.35-1.00}{3.25-1.65} = \frac{1.35}{1.60}\) = 0.84
Precautions:
I avoided parallax error in reading spring balance.
I noted zero error of spring balance.
l avoided splashing of liquid.
I avoided object touching the bottom or side beaker.
I cleaned the mass before dipping it into the liquid.
(bi) Weight of kerosine displaced = volume of object x density of kerosine x g
\(\frac{\text {Mass of object}}{\text {density of of object}}\) x density of kerosine x g
= \(\frac{20 \times 10^{-3}kg \times 8.0 \times 10^{2} kgm^{-3} \times 10ms^{-2}}{ 8.0 \times 10^{-3} kgm^{-3}}\)
= 0.02N = upthrust of the weight of object in air = mass x g
= 20 x 10\(^{-3}\) X 10 = 0.2N
Tension in the spring = weight of an object in the air - upthrust
= 0.2N - 0.02N=0.18N
The reading on the spring balance= 0.18
ii. Archimede's principle states that when a body is wholly or partially immersed in a liquid, it experiences an upthrust equal to the weight of the liquid displaced. On the other hand, the law of floatation states that a floating body displaces its own weight of the liquid in which it floats.
Source: Myschool Past Questions Archive (Record #60128)