Exam Skills & Command Words

Short Answer Words (1–2 marks)

Longer Words (Explain / Compare / Evaluate)

Key Command Words

4-Step Method (Use This Every Time)

For a “calculate” question worth 2–3 marks, write:

• 1. Formula – write the physics equation. v = d / t
• 2. Substitution – put numbers with units. v = 600 m / 30 s
• 3. Answer – calculate and round sensibly. v = 20
• 4. Units – add correct units. v = 20 m/s

If you do 1–4 clearly, you get almost all method marks even if you make a small arithmetic slip.

When It Says “Plot” or “Draw a Graph”

• Choose the correct axes:
  • x-axis – independent variable (what you change).
  • y-axis – dependent variable (what you measure).
• Use sensible scale that fills at least half the grid.
• Plot points with small neat crosses or dots.
• Draw a single smooth line or best-fit straight line – no “join-the-dots zigzag” unless instructed.

When It Says “Use the Graph to Determine…”

• Gradient (slope):
  • Pick two points far apart on the line (not necessarily data points).
  • Gradient = rise ÷ run = Δy ÷ Δx.
  • Show both points and your calculation.
• Area under graph:
  • Use rectangles/triangles or count squares.
  • Link to physics: area under v–t graph = distance, under F–d graph = work done, etc.
• Describe the relationship:
  • Straight line through origin → “directly proportional”.
  • Curved line → “non-linear” or “not directly proportional”.

Trigger Phrases

• “Describe an experiment to measure…”
• “Describe how you could investigate…”
• “Outline a practical to determine…”

When you see these, think: draw a mental diagram of the core practical, then write:

• Apparatus
• What you change (independent variable)
• What you measure (dependent variable)
• What you keep the same (controls)
• How you improve accuracy (repeat, average, zero error, etc.)

Template Answer (Example: Density of an Irregular Object)

For a 4–5 mark practical question, you could write something like:

• Measure the mass of the object using a balance.
• Fill a measuring cylinder with water and record the initial volume.
• Gently lower the object into the cylinder and record the new volume.
• Calculate the volume of the object: final volume − initial volume.
• Calculate density using ρ = m / V.

Add: “repeat and average” or “read at eye level” for extra quality.

Common Types

• “Suggest one way to improve this experiment.”
• “Suggest a reason why the results are different from the expected value.”
• “Suggest a safety precaution.”

Use common sense + the physics:

• Reduce random error → repeat readings and average.
• Reduce systematic error → check zero error, calibrate equipment.
• Reduce heat loss → insulation, lid, shiny surfaces.
• Safety → goggles, tongs, shielding, turn off power, avoid overheating.

Example Patterns

Question: “Suggest one way to improve the accuracy of the speed measurement using a stopwatch.”

• Use a longer distance so that reaction time is a smaller fraction of the total time.
• Repeat the measurement several times and take a mean.

Question: “Suggest a reason why the calculated gravitational field strength is slightly lower than 9.8 N/kg.”

• Air resistance on a falling object reduces its acceleration, so g appears smaller.
• Timing error (reaction time) when using a stopwatch.

Use a “Because… Therefore…” Chain

• Start from what changes (speed / temperature / mass / etc.).
• Use a formula or physics idea.
• End with the effect asked in the question.

Example: “Explain why a car’s braking distance increases when its speed is higher.”

• At higher speed, the car has more kinetic energy (E_k = ½ m v²).
• The brakes must remove more energy to stop the car.
• The rate at which the brakes transfer energy as heat is similar.
• Therefore it takes a longer distance for all the kinetic energy to be removed.

Example: Refraction Question

“Explain why a ray of light bends towards the normal when it passes from air into glass.”

• Glass is denser and has a higher refractive index than air.
• Light travels more slowly in glass than in air.
• The change in speed at the boundary causes the ray to change direction.
• When entering a denser medium, the ray bends towards the normal.

Notice: each sentence is one clear idea → that’s how you collect all the marks.