Essential Physics Practicals: Methods and Analysis

Posted on Nov 3, 2025 in Physics

1. Mass and Weight Relationship Investigation

Step-by-Step Procedure

  1. Attach the spring balance or Newton meter securely so it hangs vertically.
  2. Place the first known mass (e.g., 100 g) on the balance hook.
  3. Wait for the reading to stabilize and record the weight (in Newtons, N).
  4. Repeat steps 2–3 for several masses (e.g., 200 g, 300 g, 400 g).
  5. Plot a graph of weight (N) against mass (kg).

Experimental Variables

  • Independent: Mass (kg)
  • Dependent: Weight (N)
  • Control: Location (keep experiment on Earth, constant gravity)

Optimizing the Experiment

  • Use smaller increments of mass for more precise data.
  • Repeat measurements and take averages.
  • Ensure the spring balance is zeroed before measuring.

Key Physics Concepts

The relationship between weight (W), mass (m), and gravitational field strength (g) is:

W = m × g

The graph of weight versus mass is a straight line passing through the origin; the gradient of this line equals the gravitational field strength (approximately 9.8 N/kg).

Safety Precautions

  • Handle masses carefully to avoid injury.

2. Investigating Force and Spring Extension (Hooke’s Law)

Step-by-Step Procedure

  1. Fix the spring to a clamp stand vertically.
  2. Measure the original length of the spring (unstretched).
  3. Add a known weight (force, e.g., 100 g mass) and measure the new length.
  4. Calculate extension: Extension = New Length – Original Length.
  5. Add more weights incrementally, recording the extension each time.
  6. Plot force (weight) against extension.

Experimental Variables

  • Independent: Force applied (weight added, N)
  • Dependent: Extension (m)
  • Control: Spring used, room temperature

Optimizing the Experiment

  • Measure extension accurately, perhaps using a pointer and ruler.
  • Use small weight increments to capture the elastic region precisely.
  • Repeat measurements for accuracy.

Key Physics Concepts

Hooke’s Law: Force is directly proportional to extension (F ∝ x) up to the elastic limit.

The force-extension graph is a straight line through the origin up to the elastic limit, where the gradient represents the spring constant (k).

Safety Precautions

  • Do not add excessive weight; the spring may snap or be permanently deformed.

3. Determining Specific Heat Capacity

Step-by-Step Procedure

  1. Measure the mass (m) of the material (metal block or water).
  2. Insert the heater and thermometer into the material.
  3. Measure the starting temperature (T1).
  4. Turn on the heater and start the stopwatch simultaneously.
  5. Record the temperature every minute for a set time (e.g., 10 minutes).
  6. Record the voltage (V) and current (I) from the power supply.
  7. Turn off the heater and calculate the energy supplied (E) using the formula: E = V × I × t (where t is total time in seconds).
  8. Calculate specific heat capacity (c) using the formula: c = E / (m × ΔT) (where ΔT is the temperature change).

Experimental Variables

  • Independent: Time the heater is on
  • Dependent: Temperature change (ΔT)
  • Control: Mass of material, heater power, insulation quality

Optimizing the Experiment

  • Use insulation (e.g., cotton wool or lagging) to reduce heat loss to the surroundings.
  • Take frequent temperature readings to plot a reliable heating curve.
  • Ensure the heater and thermometer are fully immersed in the material.

Key Physics Concepts

Specific Heat Capacity (c): The energy required to raise the temperature of 1 kg of a substance by 1°C (or 1 K).

Heat loss to the surroundings significantly affects the accuracy of the calculated value.

Safety Precautions

  • Handle the heater carefully as it will be hot.
  • Avoid water spills near electrical equipment.

4. Investigating Resistance and Wire Length

Step-by-Step Procedure

  1. Set up the circuit: power supply, test wire, ammeter (in series), and voltmeter (in parallel across the wire).
  2. Measure the initial length of the wire (e.g., 10 cm).
  3. Turn on the power supply.
  4. Record the current (I) from the ammeter and the voltage (V) from the voltmeter.
  5. Calculate resistance (R) using Ohm’s Law: R = V / I.
  6. Change the wire length (e.g., 20 cm) and repeat steps 3–5.
  7. Repeat for multiple lengths.
  8. Plot resistance (R) against wire length (L).

Experimental Variables

  • Independent: Length of wire (L)
  • Dependent: Resistance (R)
  • Control: Wire thickness (cross-sectional area), material, temperature

Optimizing the Experiment

  • Keep the wire cool by switching off the power between readings (resistance increases with temperature).
  • Use the same wire thickness and material throughout the experiment.
  • Take multiple readings per length and calculate the average resistance.

Key Physics Concepts

Resistance is directly proportional to length (R ∝ L).

Ohm’s Law: Voltage (V) is equal to current (I) multiplied by resistance (R).

Safety Precautions

  • Do not let the wire overheat, as this can cause burns or damage the equipment.
  • Switch off the power supply when adjusting the circuit setup.

5. Analyzing Standing Waves on a String

Step-by-Step Procedure

  1. Attach one end of the string to a mechanical vibrator and run the other end over a pulley.
  2. Attach a known weight to the end hanging over the pulley to keep the string taut (setting the tension).
  3. Turn on the vibrator at a set frequency.
  4. Observe the standing waves that form.
  5. Measure the wavelength (λ)—the distance between two consecutive nodes or twice the distance between the vibrator and the first node.
  6. Record the frequency (f) from the vibrator.
  7. Calculate the wave speed (v): v = f × λ.
  8. Adjust the tension by changing the weight and repeat the measurements.

Experimental Variables

  • Independent: Frequency (f) or tension (T)
  • Dependent: Wave speed (v)
  • Control: String length, string material (mass per unit length)

Optimizing the Experiment

  • Keep the tension constant while measuring the effect of frequency changes (or vice versa).
  • Measure the wavelength carefully, ensuring you identify the nodes accurately.
  • Repeat measurements for accuracy.

Key Physics Concepts

Wave speed increases with tension.

The fundamental wave equation is: v = f × λ.

Safety Precautions

  • Ensure weights are securely attached to avoid falling or swinging.

6. Radiation and Half-life Measurement (Optional Practical)

Step-by-Step Procedure

  1. Set the Geiger counter at a fixed distance from the radioactive source.
  2. Switch on the Geiger counter.
  3. Measure the count rate (number of counts per minute).
  4. Record the count rate at regular intervals (e.g., every minute).
  5. Plot count rate versus time.
  6. Determine the half-life by finding the time taken for the count rate to halve.

Experimental Variables

  • Independent: Time (t)
  • Dependent: Count rate (Activity)
  • Control: Distance from source, shielding material

Optimizing the Experiment

  • Keep the distance between the source and the detector fixed.
  • Take multiple readings and calculate averages to minimize random error.

Key Physics Concepts

Half-life: The time required for the activity of a radioactive substance to decrease by half.

The count rate decreases exponentially over time.

Safety Precautions

  • Follow strict radiation safety guidelines (ALARA principle: As Low As Reasonably Achievable).
  • Use appropriate shielding and maintain distance from the source.