Physics

1. 1.

   A 0.20 kg ball falls from rest through 5.0 m. Ignore air resistance and use g = 9.8 m s^-2. Calculate its speed just before impact and its kinetic energy.

   [3 marks]

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. Gravitational potential energy becomes kinetic energy in the stated no-resistance model. Use a separate velocity equation to check consistency.
   2. v^2 = 2gh = 98 m^2 s^-2.
   3. v = 9.9 m s^-1 to two significant figures.
   4. Kinetic energy = mgh = 9.8 J.

   Marking points

   • v^2 = 2gh = 98 m^2 s^-2.
   • v = 9.9 m s^-1 to two significant figures.
   • Kinetic energy = mgh = 9.8 J.

   Examiner tip: Mass cancels when finding speed but is needed for the energy calculation.

2. 2.

   A cell has emf 12 V and internal resistance 1 ohm. It powers an external resistor of 5 ohms. Find the current and terminal potential difference.

   [3 marks]

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. The internal and external resistances carry the same current. The terminal voltage excludes the internal voltage drop.
   2. Total resistance is 6 ohms.
   3. I = 12/6 = 2 A.
   4. Terminal potential difference = 12 - 2(1) = 10 V.

   Marking points

   • Total resistance is 6 ohms.
   • I = 12/6 = 2 A.
   • Terminal potential difference = 12 - 2(1) = 10 V.

   Examiner tip: Use total resistance for current, then external resistance for terminal potential difference.

3. 3.

   In a double-slit experiment, wavelength = 600 nm, slit separation = 0.30 mm, screen distance = 2.0 m. Estimate fringe spacing and state a condition needed for a stable interference pattern.

   [3 marks]

   Answer explanation

   Draft walkthroughs are based on marking guidance, not independently verified derivations.

   1. Convert nanometres and millimetres to metres, then apply the small-angle fringe-spacing relation.
   2. Use w = lambda D/d with lambda = 6.0 x 10^-7 m and d = 3.0 x 10^-4 m.
   3. w = 0.0040 m = 4.0 mm.
   4. The sources must be coherent: same frequency and constant phase difference.

   Marking points

   • Use w = lambda D/d with lambda = 6.0 x 10^-7 m and d = 3.0 x 10^-4 m.
   • w = 0.0040 m = 4.0 mm.
   • The sources must be coherent: same frequency and constant phase difference.

   Examiner tip: Coherence requires a constant phase difference; same frequency alone is insufficient.

Original, unofficial practice questions from SubjectScout — not official past-paper questions.