2023 SCGS 4 IP EOY Physics ANS

1 2023 4 IP EOY SUGGESTED ANSWER SCHEME PAPER 1 (40 marks) Qn Answer Explanation 1 A All three forces form the triangle of forces in the correct order ( tip to tail) 2 D Weight decreases with decreasing g ; mass of satellite remains constant 3 C Let the initial volume of air be V cm3 Mass of air = V x 0.0012 g. Density of air at the final volume = ( 0.0012 V g )/0.5 V cm3 = 0.0024 g/cm3 4 A Acceleration is the rate of change of velocity. Car accelerates when it starts from rest and reaches zero at constant speed. 5 D The area under v-t graph of car D is the smallest. 6 D Let the time taken to accelerate by t. Thus ½ 10ms-1( 11+ 11-t) = 100 m ⇒ t =2s. Acceleration = 10 /2 ms-2 = 5.0 ms-2 7 D When parachute opens fully, the upward force is greater than the weight and the resultant force is upwards causing a sharp deceleration. Since the resultant force is upwards, the acceleration is also upwards. 8 B At constant velocity, P = Fv = 2400 N x 90 ms-1 = 2.16 x 105 W or 2.2 x 105 W ( 2 s.f.) 9 A From Fnet= ma 2000 N – R = 750 x 2.0 ⇒ R = 500 N or 0.5 kN 10 A A has the broadest base and the lowest centre of gravity. 11 A Clockwise moment = 16.0 N x (50.0 cm sin 30 o) = 400 Ncm Anticlockwise moment = 5.0 N x 50.0 cm = 250 Ncm Resultant moment -= 150 Ncm or 1.5 Nm anticlockwise 12 C Total anticlockwise moment = F x 0.5 + F x 2.5 = 3.0 F D cannot produce a larger anticlockwise moment as the force on the left is not acting at the edge of the rod, thus that force produces a smaller anticlockwise moment. 13 D Total pressure= 100000 Pa + 15x1000x10 Pa = 250 000 Pa 14 B Pgas + 60 mmHg = 756 mmHg ⇒ Pgas = 696 mmHg 15 D Pressure is the same throughout the liquid. 16 C Oil : efficiency = 200/500x 100% = 40% ; Nuclear : efficiency = 40/200x 100% = 20% ; Oil : efficiency = 9/10x 100% = 90% 17 B Using h = gain in GPE / weight , Athlete B has the highest jump of 2.3 m 18 C Decreasing volume increases the frequency of collision with the inner walls. Molecules move at the same average speed because temperature remains unchanged. Pressure increases due to more particles hitting per unit area of the inner wall. 19 A Temperature increases ⇒ molecules gain thermal energy and move faster. They move further apart, the potential energy increases. 20 C Brownian motion is the result of the unequal bombardment on all sides of a smoke particle by air molecules moving at different velocities. 21 D Recall EM waves application

2 Qn Answer Explanation 22 C After the wave have move to the right by one wavelength, both buoys would have execute one oscillation and return to their original starting position. 23 A Ultrasound is a longitudinal wave and requires a medium to propagate 24 D An echo is the repetition of a sound due to the reflection of sound 25 D Electro