Investigating Forces · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Investigating forces: fair tests and data

Science · Forces & Motion · ages 12-13
Name ______________________   Date ____________

  1. You measure the horizontal pull on a trolley moving along a level track. How should you pull so the meter reading equals that horizontal pull?

    • With a quick, sharp tug
    • Steadily, in a straight line with the trolley's motion
    • At an upward angle, lifting the trolley a little

  2. The expected pull is 8 N. Which spring newton meter has a stated range that covers this pull without exceeding its upper limit?

    • 0 to 2 N
    • 0 to 10 N
    • 0 to 5 N
    • 0 to 6 N

  3. Keeping the control variables fixed removes all measurement uncertainty from a force investigation.

    Circle one:   True   False

  4. A spring graph follows this lesson's convention: force vertically and extension horizontally. Which horizontal-axis label is correct?

    • Force (N)
    • Loaded length (cm)
    • Extension (cm)
    • Spring constant (N/cm)

  5. Priya wants to test how force affects a trolley's acceleration. Which variable should she keep the same?

    • The mass of the trolley
    • The force she applies
    • The distance the trolley travels

  6. Priya wants a 4 kg trolley to accelerate at 3 m/s². Opposing horizontal forces are negligible. What horizontal pull is required, in N?

    Answer: ______________

  7. You vary the load to measure spring extension. Which spring condition should be controlled between trials?

    • The loaded length must never change
    • The measured extension must stay fixed
    • The applied force must stay unchanged
    • Use the same undamaged spring

  8. Within its proportional range, Tom's spring extends 3 cm for each newton. What extension should 4 N produce, in cm?

    Answer: ______________

  9. A spring with k = 40 N/m extends by 0.15 m within its proportional range. Find the applied force in N.

    Answer: ______________

  10. Between two runs, Dev increases the pulling force and also swaps in a heavier trolley. The acceleration changes. What can he conclude?

    • The bigger force definitely caused the change
    • He cannot tell whether the force or the mass caused the change
    • The heavier trolley definitely caused the change
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Investigating forces: fair tests and data W1-mt_xkn2sf93WJ-s1

  1. Steadily, in a straight line with the trolley's motion · A steady horizontal pull along the meter's axis lets its tension reading equal the horizontal pull. An angled meter can still measure axial tension, but that is not solely horizontal force.
  2. 0 to 10 N · 8 N is within the 0 to 10 N range. It exceeds the upper limits of the other three meters.
  3. False · Controls reduce competing explanations. Measurements can still have uncertainty even when those conditions stay fixed.
  4. Extension (cm) · The horizontal axis represents extension, not total loaded length. Centimetres are a suitable extension unit.
  5. The mass of the trolley · Keeping mass fixed prevents a mass change from competing with the force change. Track conditions and measurement uncertainty also need checking.
  6. 12 · F = ma with m = 4kg and a = 3 m/s² gives F = 4 x 3 = 12N.
  7. Use the same undamaged spring · Use the same undamaged spring so its properties do not become a competing change. Loaded length and extension are allowed to change.
  8. 12 · The pattern adds 3cm for each newton: 3, 6, 9, 12, so 4N gives 12cm.
  9. 6 · F = kx = 40 × 0.15 = 6 N.
  10. He cannot tell whether the force or the mass caused the change · Two variables changed at once, so either one could be the cause; the test is no longer fair.
Worksheet · LightMySky