CEDAR 2025 PHY PRELIM P2 MS

1 2025 S4 Physics Prelim Mark Scheme Paper 2 Section A Qn Solution Mark 1(a)(i) 0 to 1 s and 8 to 12 s [1] (ii) 0 to 1 s, the car is at rest. 8 to 12 s, the car is moving at constant velocity or constant speed. [1] [1] (b)(i) At t = 3.0 s, total resistive force is 700 N. Fnet = forward force – total resistive force ma = 2400 – 700 800 x a = 1700 a = 2.13 m/s2 [1] [1] (ii) Fnet = ma = 800 x 0.50 = 400 N 400 = forward force – total resistive force Total resistive force = 2400 – 400 = 2000 N t = 6.8 s [1] [1] 2(a) anticlockwise moment = clockwise moment 23 x 10 x d = 60 x 1.7 230d = 102 d = 102/230 = 0.44 m [1] [1] (b)(i) Wooden barrier arm will turn anticlockwise about the pivot. The electromagnet will induce magnetism in soft iron bar A with an opposite pole , attracting and pulling it down. [1] [1] (ii) Steel bar is a hard magnetic material and will retain some magnetism that is induced in it by the electromagnet. When the switch is opened, the steel bar will remain attracted to electromagnet and the wooden barrier arm cannot return to horizontal position. [1] [1] 3(a) Ek = ½ m v2 = ½ x 700 x 402 (this step must be shown to be awarded full credit) = 560 000 J (shown) [1] (b) As the car moves up slope, all the energy in kinetic store of the car will be transferred to the gravitational potential store of the car, as well as to the internal store of the car and escape lane. [1] [1] (c)(i) Gain in Ep = mgh = 700 x 10 x 3.0 = 21 000 J [1]

2 (ii) Loss in Ek = Gain in Ep + work done to overcome friction 560 000 = 21000 + (fr x s) = 21000 + (fr x 40) fr = 13 475 = 13 500 N [1] [1] (d) Unevenness of the surface of the stones [1] 4(a)(i) Pressure is the force acting per unit area. [1] (ii) Particles of steam are moving randomly at high speed. These particles will bombard the walls of the piston with a force. The total force acting per unit area results in a pressure on piston. [1] [1] (b) Pressure difference = 2.1 x 106 – 1.0 x 105 Force/Area = 2.1 x 106 – 1.0 x 105 Force = (2.1 x 106 – 1.0 x 105) x 0.30 = 6.0 x 105 N [1] [1] 5(a) Microwave / Radiowave [1] (b) Wave speed = freq x wavelength 3.0 x 108 = 18 x 109 x λ λ = 0.017 m No of wavelengths = (560 000)/0.017 = 3.3 x 107 or 3.4 x 107 [1] [1] (c)(i) Less disruption of signal / Less degradation of signal [1] (ii) η = 1/(sin c) = 1/ (sin 45) = 1.41 or 1.4 [1] [1] (iii) Angle of incidence = angle of reflection and angle between incident ray and reflected ray > 90° (use set square/protractor to ensure) [1] 6(a) Larger percentage of energy is dissipated or wasted as heat in filament lamp [1] (b) Both have the same output power 6.2 % = (output power/input power) x 100% 6.2