Science 2019
2 questions with worked solutions · Aligned with the NIE syllabus
-
A 2 kg ball is held at rest 5 m above the ground. (Take g = 10 m/s²) (i) Calculate the gravitational potential energy of the ball. (ii) Just before the ball hits the ground (ignoring air resistance), calculate its kinetic energy. (iii) Name the energy transformation as the ball falls.
Show worked solution
(i) GPE = mgh = 2 × 10 × 5 = 100 J (ii) By conservation of energy, KE = GPE = 100 J (no energy lost to friction). (iii) Gravitational potential energy → Kinetic energy.Source: NIE O/L Science 2019 Paper II Q6 -
An electric heater of power 1 500 W heats 2 kg of water from 20 °C to 70 °C. (Specific heat capacity of water = 4 200 J/kg/°C) (i) Calculate the thermal energy absorbed by the water. (ii) Calculate the time taken by the heater (assume 100% efficiency). (iii) Explain why a metal spoon becomes hotter than a wooden spoon in the same cup of hot tea.
Show worked solution
(i) Q = mcΔT = 2 × 4200 × (70 − 20) = 2 × 4200 × 50 = 420 000 J (ii) P = Q / t → t = Q / P = 420 000 / 1 500 = 280 s (iii) Metal is a GOOD conductor of heat; free electrons transfer thermal energy quickly from the hot tea to the hand. Wood is a poor conductor (insulator); it does not transfer heat quickly, so it feels cooler.Source: NIE O/L Science 2019 Paper II Q5
Past papers are reproduced from the Department of Examinations, Sri Lanka, for educational use. The 2026 model paper and its marking scheme are original Idasara Academy work.