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AceDSE · Paper · 2026.07

物理
Physics

Modelling, Measurement and Explanation Test

minutes80 minutes
marks40 marks
Attempted componentEnglish
Candidate name
Date

Sample-paper basis

sample papers' numerical chains, circuit diagrams, graphs, experimental evaluation and elective applications

Scope of this paper

A compressed written-paper diagnostic; practical SBA remains separate.

Candidate instructions

  1. Take g=9.81 m s⁻² unless otherwise stated.
  2. Show equations, substitution and units.
  3. State assumptions when a model is used.

Question 1 — Motion and energy

14 marks
1(a)
A 1.50 kg trolley starts from rest, accelerates uniformly at 0.800 m s⁻² for 6.00 s, then brakes uniformly to rest in 4.00 s. Find its maximum speed and total distance travelled.
[6 marks]
1(b)
During acceleration, a constant resistive force of 0.300 N acts. Find the driving force and the work done by it over the first 6.00 s. Explain why this work exceeds the increase in kinetic energy.
[5 marks]
1(c)
A motion sensor records positions every 0.10 s. State how velocity at t=2.0 s could be estimated and one reason why a wider time interval is not always better.
[3 marks]

Question 2 — Sensor circuit

14 marks
2(a)
A 100 Ω resistor and an LDR are in series across an ideal 12.0 V supply. The output is measured across the 100 Ω resistor. Calculate the output in bright light (LDR 500 Ω) and darkness (LDR 5.00 kΩ).
[6 marks]
2(b)
An alarm switches on when the output falls below 0.500 V. Find the LDR resistance at the switching point and state whether this is a dark-activated alarm.
[4 marks]
2(c)
A voltmeter of resistance 1.0 kΩ is connected across the 100 Ω resistor. Explain and calculate how it changes the bright-light reading.
[4 marks]

Question 3 — Thermal transfer and waves

12 marks
3(a)
A 1.20 kW heater warms 2.00 kg water from 20.0°C to 80.0°C. Take c=4200 J kg⁻¹ K⁻¹. Calculate the ideal heating time. If the actual time is 520 s, find the efficiency over this interval.
[6 marks]
3(b)
Water waves of wavelength 4.0 cm approach a gap. Compare the diffraction when the gap is 4.0 cm and when it is 20 cm. Explain using the ratio of gap width to wavelength.
[3 marks]
3(c)
A student says doubling wave frequency must double wave speed. Evaluate the claim for waves in the same uniform medium.
[3 marks]

Every question and figure is original AceDSE work; official samples were used only to calibrate format, complexity and reasoning depth.
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