Communicate experimental results orally

1. Identify the Variables

• Independent variable: The variable you change deliberately (usually plotted on the x-axis)
• Dependent variable: The variable you measure that changes because of the independent variable (usually plotted on the y-axis)

2. Describe the Pattern Shown by the Graph

Look at the shape of the graph and describe it in words:

• Straight line through the origin: Direct proportion — as one variable increases, the other increases proportionally
• Straight line not through the origin: Linear relationship — $y = mx + c$
• Curve that levels off: Approaches a maximum value
• Hyperbola (curve getting closer to axes): Inverse proportion — as one variable increases, the other decreases

3. State the Mathematical Relationship

From the graph, determine the equation that relates the two variables. This often involves identifying:

• The gradient (slope) if the relationship is linear
• The constant of proportionality

4. Speak Clearly and Logically

When presenting orally, follow this structure:

1. State what the experiment investigated
2. Identify what was varied (independent variable) and what was measured (dependent variable)
3. Describe the shape of the graph
4. State the mathematical relationship
5. Give a brief conclusion

A Form 2 class investigated how the extension ($x$) of a rubber band changes when different loads ($F$) are hung from it. Their results are shown in the table:

Step 1: Plot the graph

When you plot load on the x-axis and extension on the y-axis, you get a straight line passing through the origin.

Step 2: Describe orally what the graph shows

"In this experiment, we investigated how the extension of a rubber band changes with the load applied. The load was the independent variable, and the extension was the dependent variable. The graph is a straight line that passes through the origin."

Step 3: State the mathematical relationship

The extension doubles when the load doubles. This is a direct proportion relationship. From the graph:

$F \propto x$

The gradient is $0.5\ \text{N/cm}$, so:

$F = 0.5x$

or

$x = 2F$

Step 4: Complete oral presentation

"In conclusion, the extension of the rubber band is directly proportional to the load applied. For every 1 newton of load, the rubber band extends by 2 centimeters. This relationship can be written as $F = 0.5x$ or $x = 2F$."

Use these phrases when describing graphs:

• "The graph shows a linear relationship between..."
• "There is a direct proportion between the two quantities."
• "As [variable] increases, [variable] decreases in an inverse relationship."
• "The line passes through the origin, indicating..."
• "The gradient of the graph equals..."

• Work in pairs: one student explains the graph while the other listens and checks for accuracy
• Practice describing graphs from different physics experiments
• Always connect what you see on the graph to the physics concept being investigated
• Use correct scientific terminology but keep your explanation clear

In Tanzania, farmers use simple experiments to test how different amounts of fertilizer affect crop yield. By plotting graphs of fertilizer amount versus harvest weight, a farmer can describe orally to agricultural officers whether more fertilizer always means more yield, and identify the optimal amount to use. This helps them make informed decisions about how much fertilizer to buy — saving money while maximizing their maize or rice harvest for the market.