- Fix the 100g mass marked P at B, the 80 cm mark of the uniform metre rule, using an adhesive.
- Suspend another 100g mass marked Q at A, a distance V = 10.Ocm from the 0 cm mark of the metre rule.
- Balance the whole arrangement horizontally on a knife edge as shown in the diagram above.
- Measure and record the distance U of K from the 0 cm mark of the metre rule.
- Repeat the procedure for five other values of V = 15.0, 20.0, 25.0, 30.0 and 35.0 cm
- In each case, measure and record the Corresponding values of U. Tabulate your readings.
- Plot a graph of U on the vertical axis against V on the horizontal axis.
- determine the:
(1) slope, s, of the graph
(2) intercept c, on the vertical axis. - Evaluate (i) K\(_{1}\) =\(\frac{(1 – 2s)}{s}\) 100:
(ii) K\(_{2}\) = \(\frac{2c}{s}\) – 160 - State two precautions taken to ensure an accurate result
(b)i. State two conditions under which a rigid body at rest remains in equilibrium when acted upon by three non-parallel coplanar forces.
ii. Explain how the position of the centre or gravity of a body affects the equilibrium of the body.
Explanation
Table of values
| Vcm | Ucm |
| 10.0 | 47.0 |
| 15.0 | 48.3 |
| 20.0 | 49.4 |
| 25.0 | 51.20 |
| 30.0 | 52.50 |
| 35.0 | 54.00 |
Slope = \(\frac{Du}{DN} = \frac{13}{47}\) = 0.28
The intercept (c) on the vertical axis = 44cm
(i) K\(_{1}\) = \(\frac{(1-2s)}{s}\)100 = \(\frac{1-0.56}{0.28}\)100 = 157
(ii) K\(_{2}\) = \(\frac{2c}{s}\) - 160 = \(\frac{2 \times 44}{0.28}\) - 160 = 154.3
Precautions:
- I Avoid draught.
- I Ensure mass does not rest on the table
- I avoid errors due to parallax when reading metre rule.
(b)i. The conditions under which a rigid body remains in equilibrium when acted upon by three non-parallel coplanar forces are:
- The forces must be concurrent (i.e. they must meet at a point.
- The resultant of the forces must be equal to zero.
- The forces can be represented in magnitude and direction by the sides of a triangle taken in order.
- A body is in stable equilibrium if the vertical line through the centre of gravity falls outside the base of support when the body is slightly titled