Investigating Newton’s Second Law

 

Investigating Newton’s Second Law Using the Horizontal and Vertical Ball Launcher – Which Ball Hits the Ground First?

Newton’s Second Law links force, mass, and acceleration — but it also explains one of the most surprising results in physics: a ball fired horizontally and another dropped vertically hit the ground at the same time, provided they start at the same height. This simple but elegant experiment helps students connect equations of motion to real-world outcomes.

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The Experiment

Using a ball launcher, one ball is released vertically downward while another is launched horizontally from the same height. Students use strobe flash or high-speed video to measure the time each takes to hit the ground.

Observation:
Both balls land simultaneously — despite one moving sideways.

This happens because horizontal motion and vertical motion are independent. Gravity accelerates both balls downward at the same rate (about 9.8 m/s²), regardless of their horizontal speed. Mass has nothing to do with the equation and forces that work at right angles to one another are ignored.

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The Science

The experiment illustrates the core of Newton’s Second Law:

$$F = ma$$

Gravity provides the same downward force on both balls, giving them equal acceleration.
The horizontally launched ball has an additional velocity component, but that motion does not affect how long gravity takes to pull it to the ground.

This principle lies behind projectile motion and explains why a bullet fired from a gun and one dropped from the same height (in a vacuum) would hit the ground together.

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Skills Highlight

• Applying $F = ma$ to explain motion in two dimensions

• Recording and analysing motion data using sensors or video frames

• Understanding the independence of horizontal and vertical motion

• Using experiments to test theoretical predictions

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Why It Works in Teaching

This investigation transforms abstract equations into a striking visual demonstration of Newton’s laws. Students often predict that the fired ball will take longer to fall — until they see the data prove otherwise. It’s one of those memorable experiments that makes physics click.

 

Investigating Enzyme Inhibitors Using Catalase

Enzymes are biological catalysts that control reactions in living organisms, but their activity can be slowed or stopped by inhibitors. Using catalase — an enzyme found in many living tissues — students can explore how inhibitors affect enzyme activity and reaction rates.

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The Experiment

Catalase breaks down hydrogen peroxide into water and oxygen:

$$2H_2O_2 \rightarrow 2H_2O + O_2$$

Students can measure the volume of oxygen produced or the height of foam formed when hydrogen peroxide reacts with catalase from liver or potato extracts.

To investigate inhibition:

• Add a competitive inhibitor such as copper sulfate, which competes with the enzyme’s active site.

• Add a non-competitive inhibitor like lead nitrate, which alters the enzyme’s shape.

• Compare reaction rates with and without inhibitors at controlled temperature and pH.

Method 1: Measuring oxygen production

This method measures the rate of the reaction by quantifying the amount of oxygen produced. 

Materials: You will need a catalase source (e.g., yeast, liver, or potato), hydrogen peroxide, a source of inhibitor, test tubes or a conical flask, a gas syringe or ruler to measure foam, and a stopwatch.

• Set up the experiment: Place the hydrogen peroxide solution in a test tube or flask. Prepare the enzyme solution by grinding potato with distilled water or using a liquid source like yeast suspension.
• Introduce the inhibitor: Add a specific concentration of the inhibitor to the hydrogen peroxide solution. Repeat the experiment with different concentrations of the same inhibitor, and also run a control without any inhibitor.
• Start the reaction: Add the enzyme solution to the hydrogen peroxide and inhibitor mixture and immediately start the stopwatch.
• Measure the product: Collect the oxygen gas produced in the gas syringe and record the volume at set time intervals, or measure the height of the foam produced.
• Analyze the results: A slower reaction rate (less oxygen produced or lower foam height in a given time) indicates a more effective inhibitor.

Method 2: Using a filter paper disk (for qualitative analysis) 

This is a simpler method, often used for a qualitative or comparative investigation. 

Prepare the enzyme: Make a paste from a source of catalase, such as a potato, and suspend it in a small amount of distilled water.

• Prepare the substrate: Place a solution of hydrogen peroxide in a specimen tube.
Prepare the filter paper disks: Dip small filter paper disks into the catalase suspension and tap off any excess liquid.
Add the inhibitor: Apply a drop of the inhibitor to one of the filter paper disks. You can also test disks without any inhibitor (control) and disks with different inhibitors.
Start the reaction: Drop the treated disk into the hydrogen peroxide solution and time how long it takes for the disk to sink to the bottom. The time it takes for the disk to sink is inversely proportional to the enzyme activity.
Analyze the results: If the inhibitor is effective, the disk will sink faster because the catalase is less active.

Prepare reagents: Measure the rate of product formation using a spectrophotometer to measure the absorption of light.

Substrate concentration: Keep the concentration of hydrogen peroxide constant across all experiments.

Method 3: Spectrophotometric analysis 

Prepare reagents: Measure the rate of product formation using a spectrophotometer to measure the absorption of light.

• Run the experiment: Place the reaction mixture in a cuvette and measure the light absorption of the product at a specific wavelength.
• Introduce the inhibitor: Add the inhibitor and record the change in light absorption over time.
• Analyze the results: A significant change in the rate of light absorption indicates the inhibitor is effective.
• Key variables to control and investigate 
• This is the easiest to do in a short lesson when results are required quickly and using a @pascoscientific Colorimeter works well.

• Substrate concentration: Keep the concentration of hydrogen peroxide constant across all experiments.
• Enzyme concentration: Ensure the concentration of the catalase is the same for all trials.
• pH and temperature: Maintain a constant pH and temperature, or investigate how inhibitors affect the enzyme activity at different temperatures or pH levels.
• Inhibitor concentration: Vary the concentration of the inhibitor to determine its effect on enzyme activity and to calculate the
  

  $I{C}_{50}$
  value (the concentration of inhibitor required to halve the enzyme activity). 

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The Science

Enzyme inhibitors reduce the rate of reaction in two main ways:

• Competitive inhibitors occupy the enzyme’s active site, blocking the substrate.

• Non-competitive inhibitors bind elsewhere, changing the enzyme’s structure so the substrate no longer fits.

By plotting rate against inhibitor concentration, students can see how the rate decreases and learn how enzymes are regulated in cells — and how poisons and drugs work.

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Skills Highlight

• Designing fair tests with controlled variables

• Measuring reaction rates quantitatively using gas volume or sensor data

• Analysing graphs to interpret inhibition types

• Linking enzyme structure to biochemical function

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Why It Works in Teaching

This investigation links practical biochemistry to real-world contexts such as medicine and toxicology. Students can visualise enzyme action, inhibition, and the importance of active site shape — core ideas that underpin much of biology.

 

Logic Gates – Using Real Gates and Investigating Their Properties

Digital systems form the backbone of modern computing, and logic gates are the building blocks that make them work. By using real electronic gates rather than just truth tables on paper, students can see how logic becomes hardware.

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The Experiment

Students connect AND, OR, and NOT gates using logic gate ICs or simulation boards. LEDs on the outputs show when a gate produces a “1” (true) or “0” (false).

Typical activities include:

• Testing each gate with all input combinations and recording the results.

• Constructing combinations of gates, such as NAND and NOR, to show universality.

• Comparing logic circuit behaviour with truth tables.

• Using PASCO voltage sensors or simple voltmeters to measure input and output levels quantitatively.

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The Science

Each gate performs a basic logical operation:

• AND gate: Output is high only if both inputs are high.

• OR gate: Output is high if at least one input is high.

• NOT gate: Inverts the input signal.

By combining these, more complex functions like adders and flip-flops can be built. Logic circuits operate using voltage thresholds rather than symbolic logic, linking abstract reasoning to real electronics.

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Skills Highlight

• Building and testing circuits with real logic components

• Recording truth tables and verifying logic behaviour

• Understanding how logic connects to binary decision-making in computing

• Seeing how simple circuits scale up to processors and memory units

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Why It Works in Teaching

Logic gates bring computing to life. Students can see lights switch on and off in response to logical conditions, reinforcing their understanding of Boolean algebra and digital systems. It’s the perfect bridge between abstract logic and real-world technology.

 

Testing for Ions – Flame Tests and Precipitation Reactions

One of the most colourful areas of chemistry is qualitative analysis — identifying unknown ions through characteristic colours and precipitates. With simple reagents and a Bunsen burner, students can turn invisible chemistry into visible results.

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Flame Tests

Different metal ions emit distinctive colours when heated in a flame because their electrons absorb energy and then release it as light of specific wavelengths.

Typical results:

Metal Ion	Flame Colour
Lithium (Li⁺)	Crimson red
Sodium (Na⁺)	Yellow
Potassium (K⁺)	Lilac
Calcium (Ca²⁺)	Orange-red
Copper (Cu²⁺)	Green-blue

Students clean a wire loop in hydrochloric acid, dip it into the sample, and hold it in the flame to identify the metal by its colour.

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Precipitation Reactions

For non-metal anions and transition metal cations, adding reagents produces coloured or white precipitates:

Examples:

• Add sodium hydroxide solution to identify metal hydroxides:

  • Copper(II): blue precipitate

  • Iron(II): green precipitate

  • Iron(III): brown precipitate

• Add silver nitrate solution to identify halides:

  • Chloride: white precipitate

  • Bromide: cream precipitate

  • Iodide: yellow precipitate

Each reaction gives students visible confirmation of the ions present.

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Skills Highlight

• Carrying out flame tests and chemical analysis safely

• Recording results accurately using observation tables

• Understanding ionic equations and solubility rules

• Linking colour changes to electron transitions and compound structure

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Why It Works in Teaching

Flame tests and precipitation reactions appeal to all senses — colour, pattern, and chemical reasoning. They help students connect observations with ionic theory, building confidence in practical skills and understanding of chemical identity.

 

Using PASCO Force Sensors to Study Impulse and Momentum

Impulse and momentum are central ideas in mechanics, linking force and motion in real, measurable ways. Using PASCO force sensors, students can record how forces change during a collision and see how impulse equals the change in momentum.

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The Experiment

A PASCO force sensor is attached to a dynamics cart or collision block on a track. When the cart collides with a spring bumper or another cart, the sensor records the force-time graph.

Students can then calculate the impulse by finding the area under the force-time curve:

$$\text{Impulse} = \int F\,dt = \Delta p = m(v - u)$$

where $m$ is the mass of the cart, and $u$ and $v$ are the initial and final velocities.

The data show that even though force varies during the collision, the total impulse equals the change in momentum.

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The Science

Impulse describes how a force acting over a time interval changes momentum.

• A large force acting briefly can have the same effect as a small force acting for longer.

• Momentum is always conserved when no external forces act — an essential principle in both linear and two-dimensional collisions.

By comparing different materials, bumpers, or collision speeds, students can see how impulse spreads over time to reduce peak force — the same principle used in crumple zones and safety equipment.

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Skills Highlight

• Using sensors to record time-resolved force data

• Calculating impulse from graphs and comparing it with measured momentum change

• Interpreting conservation of momentum in real systems

• Relating physics to real-world safety design and engineering

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Why It Works in Teaching

PASCO force sensors transform an invisible concept into a measurable one. Students don’t just accept that impulse equals the change in momentum — they prove it by analysing real data and connecting mathematical models to physical events.

 

Modelling Epidemics with Exponential Functions

Biology meets Maths: Exponential functions aren’t just abstract curves on a graph — they describe some of the most important processes in nature and society. One of the clearest examples is how infectious diseases spread through a population. By modelling epidemics mathematically, students can see how small changes in rate lead to dramatic differences in outcome.

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The Concept

When a disease spreads, the number of infected people can grow rapidly because each infected individual passes it on to more than one other person. This creates an exponential pattern, expressed as:

$$N(t) = N_0 e^{rt}$$

where:

• $N_0$ = initial number of infected people

• $r$ = rate of infection

• $t$ = time (days, weeks, etc.)

• $N(t)$ = total number of infected individuals at time $t$

The model predicts fast early growth that later slows as immunity builds or control measures reduce the spread.

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Classroom Activity

Students can use spreadsheet or Python tools to:

• Plot infection growth for different $r$ values

• Compare exponential and logistic models (with a population limit)

• Discuss how interventions such as vaccination or isolation alter the shape of the curve

This turns a simple mathematical equation into a real-world tool for understanding public health.

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Skills Highlight

• Applying exponential growth models to real-world contexts

• Analysing how rate constants affect curve steepness

• Using technology to visualise and interpret data

• Understanding the limitations of models and the effect of assumptions

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Why It Works in Teaching

Modelling epidemics gives exponential functions real meaning. Students see that what starts as a small number can grow rapidly under the right conditions — and that mathematics helps predict, explain, and manage such events.

Investigating Resonance in Springs and Pendulums

Resonance is one of the most fascinating concepts in physics — when a system vibrates with maximum amplitude because it is driven at its natural frequency. Using springs and pendulums, students can observe resonance directly and understand why it is both useful and potentially destructive in the real world.

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The Experiment

Students set up a mass-spring system and a simple pendulum, each free to oscillate. A driver system (a mechanical vibrator or small motor) applies periodic forces at different frequencies. Lascells make a fantastic model for this, which is set up such that the strings are not tangled, and the experimental setup is immediately ready to go.

As the driving frequency changes, the amplitude of oscillation varies:

• At low or high frequencies, motion is small.

• At the natural frequency, amplitude increases dramatically — this is resonance.

The same can be shown using multiple pendulums of different lengths coupled by a thread; when one is set swinging, only the pendulum with the same natural frequency begins to move significantly.

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The Science

Resonance occurs when the frequency of a driving force matches the system’s natural frequency. Energy transfer is most efficient at this point, leading to a large increase in amplitude.

Key relationships:

$$f = \frac{1}{2\pi}\sqrt{\frac{k}{m}} \quad \text{for a spring}$$ $$f = \frac{1}{2\pi}\sqrt{\frac{g}{l}} \quad \text{for a pendulum}$$

These equations show that the frequency depends on mass (for springs) and length (for pendulums).

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Skills Highlight

• Measuring oscillation frequency using timers or counting

• Plotting amplitude against driving frequency to identify resonance peaks

• Applying formulae to predict natural frequencies

• Understanding the practical implications of resonance in bridges, buildings, and musical instruments

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Why It Works in Teaching

Resonance links theory to experience — students can feel, hear, and see it. The rising amplitude at resonance provides an immediate visual and physical demonstration of a key principle of oscillatory motion, while the equations connect it back to quantitative analysis.