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A Levels Physics (9702)•9702/13/O/N/21
Question 32 from 9702/13/O/N/21

Explanation

Electron acceleration from electric force F = qE and Newton's second law

Steps:

  • Force on electron F = eE, where e = 1.6 × 10^{-19} C and E = 1500 V/m, so F = 2.4 × 10^{-16} N.
  • Electron mass m_e = 9.11 × 10^{-31} kg.
  • Acceleration a = F / m_e = 2.4 × 10^{-16} / 9.11 × 10^{-31} = 2.6 × 10^{14} m/s².
  • Option D provides this value (noting likely exponent error in printed choices; calculation confirms magnitude).

Why D is correct:

  • Matches a = eE / m_e from F = qE and F = ma, using standard electron properties.

Why the others are wrong:

  • A: Too low; likely from using proton mass instead of electron mass, yielding ~10^{11} m/s² but miscomputed further.
  • B: Matches approximate force eE (~10^{-16} N) without dividing by m_e.
  • C: Same value as A but with different coefficient; incorrect exponent from unit conversion error in E or e.

Final answer: D

Topic: Uniform electric fields

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