AS Level Physics chapter 1: Physical quantities and units MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

86 exam-style questions on Physical quantities and units, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

86 questions · 4 topics · 10 per test

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What chapter 1 covers

Ten Physical quantities and units questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. Which quantity is an SI base quantity?

  1. A
    force
  2. B
    energy
  3. C
    electric current
  4. D
    charge
Show answer

Answer: C. The base quantities are mass, length, time, current, temperature, amount of substance and luminous intensity. Force, energy and charge are derived.

2. Which estimate is NOT reasonable?

  1. A
    the weight of a 1.0 kg bag of sugar is about 1 N
  2. B
    the speed of sound in air is about 330 m s−1
  3. C
    room temperature is about 293 K
  4. D
    the mass of 1 litre of water is about 1 kg
Show answer

Answer: A. Weight = mg = 1.0 × 9.81 ≈ 10 N, not 1 N; mass and weight are different quantities. The other three estimates are sensible.

3. A ball moving east at 4.0 m s−1 hits a wall and rebounds west at 3.0 m s−1. What is its change in velocity?

  1. A
    1.0 m s−1 east
  2. B
    1.0 m s−1 west
  3. C
    7.0 m s−1 east
  4. D
    7.0 m s−1 west
Show answer

Answer: D. Taking east as positive: Δv = final − initial = (−3.0) − (+4.0) = −7.0 m s−1, i.e. 7.0 m s−1 west.

4. A student runs up a flight of stairs in a school building. Which is the best estimate of the useful power she develops?

  1. A
    6 W
  2. B
    60 W
  3. C
    600 W
  4. D
    6000 W
Show answer

Answer: C. Mass about 60 kg, height about 3 m, time about 3 s: P = mgh/t = 60 × 9.81 × 3 ÷ 3 ≈ 600 W.

5. The density of aluminium is 2.7 g cm−3. What is this in kg m−3?

  1. A
    0.27 kg m−3
  2. B
    2.7 kg m−3
  3. C
    270 kg m−3
  4. D
    2700 kg m−3
Show answer

Answer: D. 1 g = 10−3 kg and 1 cm3 = (10−2 m)3 = 10−6 m3, so 2.7 g cm−3 = 2.7 × 10−3 ÷ 10−6 = 2700 kg m−3. Forgetting to cube the centi gives 0.27.

6. A current of 50 μA flows for 2.0 ms. How much charge passes?

  1. A
    1.0 × 10−10 C
  2. B
    1.0 × 10−7 C
  3. C
    1.0 × 10−4 C
  4. D
    1.0 × 10−1 C
Show answer

Answer: B. Q = It = (50 × 10−6)(2.0 × 10−3) = 1.0 × 10−7 C. Treating μ as nano gives 10−10 C; ignoring the milli gives 10−4 C.

7. An ammeter reads 0.02 A when no current flows. With a potential difference of 6.0 V across a resistor, the ammeter reads 0.52 A. What is the resistance of the resistor?

  1. A
    11.1 Ω
  2. B
    11.5 Ω
  3. C
    12.0 Ω
  4. D
    12.5 Ω
Show answer

Answer: C. The true current is 0.52 − 0.02 = 0.50 A, so R = 6.0 ÷ 0.50 = 12.0 Ω. Ignoring the zero error gives 6.0 ÷ 0.52 = 11.5 Ω.

8. Which quantity has SI base units kg m2 s−2?

  1. A
    force
  2. B
    momentum
  3. C
    power
  4. D
    work done
Show answer

Answer: D. Work = force × distance = (kg m s−2)(m) = kg m2 s−2. Power is kg m2 s−3 and momentum kg m s−1.

9. Car P travels due east at 20 m s−1. Car Q travels due west at 15 m s−1. What is the velocity of Q relative to P?

  1. A
    5 m s−1 east
  2. B
    5 m s−1 west
  3. C
    35 m s−1 east
  4. D
    35 m s−1 west
Show answer

Answer: D. vQ − vP with east positive: (−15) − (+20) = −35 m s−1, i.e. 35 m s−1 west. Subtracting the speeds as scalars gives the 5 m s−1 options.

10. Which is the best estimate of the kinetic energy of a car travelling on a motorway?

  1. A
    5 × 102 J
  2. B
    5 × 103 J
  3. C
    5 × 105 J
  4. D
    5 × 107 J
Show answer

Answer: C. Mass about 1000 kg, speed about 30 m/s: KE = ½ × 1000 × 302 = 4.5 × 105 J.

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Ways to practise this chapter

Physical quantities and units: questions students ask

How many Physical quantities and units MCQs are there?

86, each with the answer and a short explanation, across 4 topics: Physical quantities, SI units, Errors and uncertainties, Scalars and vectors. Every chapter test draws ten of them, so you can take it many times.

Is the AS Level Physics chapter 1 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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