SP Unit 1.1
Practical
Basic physics
SP Unit 1.1PracticalBasic PhysicsLearners should be able to demonstrate and apply their knowledge and understanding of: |
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|---|---|
| 1. | Determination of the Density of Solids |
| 2. | Determination of unknown masses by using the principle of moments |
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1. Determination of the Density of Solids
- ⇒ Aim:
- To determine the density of a solid object using its mass and volume.
- ⇒ Apparatus:
- – Solid object (regular or irregular)
- – Top-pan balance (for mass measurement)
- – Vernier calipers/micrometer screw gauge (for regular-shaped objects)
- – Measuring cylinder (for irregular-shaped objects)
- – Water
- – String (if necessary)
- Figure 1 Determination of the density of Solids
- ⇒ Theory:
- Density (ρ) is defined as:
- [math]\rho = \frac{\text{Mass} \ (m)}{\text{Volume} \ (V)}[/math]
- ⇒ Procedure:
- For Regular-shaped Solids (e.g., cube, sphere, cylinder):
- 1. Measure Mass:
- – Use a top-pan balance to measure the mass (m) of the object accurately.
- 2. Measure Dimensions:
- – Use vernier calipers/micrometer screw gauge to measure dimensions (length, width, height, radius, etc.).
- – Calculate volume (V) using geometrical formulas. For example:
- Cube: [math]V = l^3[/math]
- Cylinder: [math]V = πr^2 h[/math]
- Sphere: [math]V = \frac{4}{3} πr^3[/math]
- 3. Calculate Density:
- [math]ρ = \frac{m}{V}[/math]
- ⇒ For Irregular-shaped Solids:
- 1. Measure Mass:
- – Use the balance to measure the object’s mass (m).
- 2. Measure Volume (Displacement Method):
- – Fill a measuring cylinder with water and note the initial volume ( [math][/math]).
- – Tie the solid with string and immerse it fully in the water.
- – Record the new volume ([math]V_2[/math] ).
- – Volume of the object = [math]= V_2 – V_1[/math]
- 3. Calculate Density:
- [math]\rho = \frac{m}{V_2 – V_1}[/math]
- ⇒ Precautions:
- – Avoid parallax error when taking readings.
- – Ensure the solid is fully submerged (for irregular solids).
- – Dry the object before measuring mass.
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2. Determination of Unknown Masses by Using the Principle of Moments
- ⇒ Aim:
- To determine the unknown mass using the principle of moments.
- ⇒ Apparatus:
- – Uniform meter rule
- – Knife edge or pivot
- – Known masses (slotted weights)
- – Unknown mass
- – Thread and hanger
- Figure 2 Determination of unknown masses by using the principle of moments
- ⇒ Theory:
- Principle of Moments: In equilibrium:
- ∑Clockwise Moment = ∑Anticlockwise Moment
- Moment = Force × Perpendicular distance from pivot.
- ⇒ Procedure:
- 1. Balance the Meter Rule:
- – Place the meter rule on a knife edge and locate its center of gravity (C.G.) — it balances horizontally when C.G. is at the pivot.
- 2. Attach Masses:
- – Suspend the known mass (m₁) at a measured distance (d₁) from one side of the pivot.
- – Suspend the unknown mass (m₂) at a distance (d₂) on the other side.
- 3. Achieve Equilibrium:
- – Adjust the positions until the meter rule balances.
- 4. Apply Principle of Moments:
- [math]m_1 × d_1 = m_2 × d_2[/math]
- Rearrange to calculate:
- [math]m_2 = \frac{m_1 \times d_1}{d_2}[/math]
- ⇒ Precautions:
- Ensure the meter rule is horizontal at equilibrium.
- Avoid friction at the pivot point.
- Take multiple readings for accuracy