You are provided with a metre rule, a knife edge, two pieces of thread and two masses \(m_1\) and \(m_2\)
Record the values of \(m_1\) and \(m_2\).
Balance the metre rule horizontally on the knife edge and record the balance point G.
With the knife edge at the 60 cm mark of the metre rule, suspend \(m_1\) at the 20 cm mark and \(m_2\) at a suitable mark such that the rule balances horizontally as illustrated in the diagram above.
Record the positions Y of \(m_1\) and Q of \(m_2\).
Evaluate 1= P - Y and d = Q - P
Repeat the procedure for four other positions of m, at 18, 16, 14 and 12 cm marks.
In each case, evaluate and record l and d.
Tabulate your readings.
Plot a graph of l on the vertical axis against d on the horizontal axis.
Determine the slope of the graph.
State two precautions taken to ensure accurate results.
(b}i. With the aid of a diagram, indicate the forces acting on the metre rule in the experimental set-up above.
ii. Define moment of a force about a point and state its S.1. unit.
Verified Correct Answer: .
Physical Principles & Numerical Solution
\(M_1\) = 20.0g
\(M_2\) = 50.0g
C.G = 50CM
S/N
L=P - Y (cm)
d = =Q - P (cm)
Y (cm)
1
40.00
37.00
20.00
2
42.00
37.50
18.00
3
44.00
38.30
16.00
4
46.00
38.70
14.00
5
48.00
39.30
12.00
Slope (s) = \(\frac{\bigtriangleup {L}}{\bigtriangleup {d}} = \frac{48-4}{39.2-28.2} = \frac{44}{10.4}\) = 4.23
Precautions:
Ensure that there is no air interference when determining the position of the centre of gravity (G) of the metre-rule.
Ensure that the suspended mass did not touch the table
Avoid error due to parallax when reading the metre rule.
Zero error of the metre rule must be noted.
(b)i.
ii. The moment of a force about a point is the product of the force and the perpendicular distance from the point to the line of action of the force. It is also defined as the turning effect of the force about a point. It is measured in Nm - SI unit.
Source: Myschool Past Questions Archive (Record #60082)