2024 BSS 4E Physics Ans Final

1 BSS/24/Preliminary Examination/4E Physics [Turn over 2024 BSS 6091 S4E Physics Preliminary Examination Mark Scheme Paper 1 ‘BCCCA’ ‘ADABC’ ‘DACDB’ ‘DBCBB’ ‘ABCAB’ ‘'BCCCB’ ‘DBDCC’ ‘DCAAC’ Qsn Answer Explanation 1 B Displacement has direction and is a vector quantity. 2 C 128 TB = 128 x 1012 B = 1.28 x 1014 B 3 C Point A - lowest point on ground, velocity zero as object is changing direction. Point B – just before going back up (velocity already changed to going upwards) Point C – object is at the highest point after first bounce Point D – object moves back down, velocity increases 4 C Object falling through air decelerate and reach a terminal velocity that is lesser than velocity of object in vacuum. 5 A Using Newton’s 2nd law, Fnet = ma 2000 – resistive force = 750 x 2.0 Resistive force = 500 N 6 A Action reaction force of weight (force by earth on box) is the force by box on earth. 7 D Object moving in a constant speed in a straight line has no change in speed and direction, hence no acceleration and no resultant force. 8 A Taking moments about F3, F1 x d1 = F2 x d2 Since d1 is smaller than d2 , F1 is larger than F2 9 B Pressure at surface of mercury = pressure at same level at column 76 cm Hg = 1200gX + 74 cm Hg 1200gX = 2 cm Hg 1200gX = 13600 g (0.02) X = 0.227 m 10 C ½ mv2 = mgh 32000 = 40 g (20) g = 40 N/kg W = mg = (40)(40) = 1600 N = 1.6 kN 11 D Power = work done / time 12 A When temperature increases, KE increases Frequency of collisions of air molecules with smoke particles increases, causing the smoke particles to change direction more frequently. 13 C Less space to move, particles collide with each other and the wall more frequently causing pressure to increase. 14 D It takes one year to pay back the cost of installation. 15 B The cooling fins increases the exposed surface area for heat to be dissipated quickly to the environment. Metal is a material used to increase rate of conduction, normally painted black to increase rate of radiation. 16 D Energy supplied = Energy used to melt salt Pt = m lf 175 × (700 – 300) = 0.50 × lf lf = 175 × (700 – 300) ÷ 0.50 = 140 000 J/kg = 1.4 × 105 J/kg 17 B decreasing the humidity (reduce moisture in air) surrounding the liquid and increasing the temperature of the liquid increases the rate of evaporation 18 C Wavelength between 2 successive compressions = 15 x (2/3) = 10 cm Speed = wavelength/period = 10 / 2 = 5 cm/s 19 B At time = 0, the particle is at the equilibrium position and moves downwards as the wave moves to the right. 20 B Frequency halved, time taken for one complete oscillation is longer. Loudness remains constant, amplitude does not change.

2 BSS/24/Preliminary Examination/4E Physics [Turn over 21 A Signals transmitted to satellite via microwaves has the longest wavelength. 22 B n = sin p/sin r