CHIJ Sec 2024 4N Prelim Ans

Ans P1 1 2 3 4 5 6 7 8 9 10 D A C D D C A C A D 11 12 13 14 15 16 17 18 19 20 C D A A C A A A B A P2 Section A 1 a) Weight is a vector quantity whereas mass is a scalar quantity. OR any relevant answers b) Density = mass/volume, volume = mass/density = 0.65/780 = 0.0008 m3 2 a) 0 – 6 s : uniform acceleration 6 – 12 s = constant velocity/speed b) acceleration = 22/6 = 3.67 m/s2 c) F = ma, m = F/a = 1800/3.67 = 490 N d) air resistance/friction 3 a) chemical potential store b) The chemical potential store in the battery is transferred electrically to the motor. Energy is transferred mechanically by a force (motor) to become kinetic energy. c) KE = ½ mv2 KE = ½ x 70 x 42 = 560 J 4 a) i) conduction ii) convection b) As the water at the bottom is heated up by the fire, it expands, becomes less dense and rises. The cooler water which is denser will sink and replace the heated water. A convection current is set up.

c) When the temperature rises, the particles will gain in kinetic energy. They move further from one another. 5 a) It is an imaginary line that join all the points that are in phase. b) decreases, decreases Section B 6 a) i) A2 = 0.25 A A3 = 0.25 A V2 = 9.0 V ii) R = V/I = 9/0.25 = 36 ohm iii) P = VI = 3 x 0.25 = 0.75 W b) i) 0 A ii) When the metal casing becomes live due to the fault, a large current will pass through the live wire and melt the fuse. iii) Beside cutting oƯ the current supply, it can also cut oƯ the high voltage supply in the live wire. 7 a) b) i) 2 half-lives ii) 5700 x 2 = 11400 years c) an electron. d) To reduce the exposure time. name of particle number of particles relative charge of particle electron 6 -1 neutron 8 0 proton 6 +1