2024 DHS Promo Physics H2 Answers

DUNMAN HIGH SCHOOL 2024 PHYSICS H2 (YEAR 5) 1 For Internal Use Only Suggested Answers to Promotional Exam Paper 1 1 2 3 4 5 6 7 8 9 10 C D C B A C A D B D 11 12 13 14 15 C D C B A 1 C The size of a hydrogen atom is around 1 Angstrom or 1010− m. 2 D Student D’s value for 𝑔 = 8.46 ± 0.05 m s−2 is far from the actual value of 9.81 but is the most precise of all the students. 3 C The resultant acceleration is due to the resultant force of air resistance and the weight of the ball 4 B N and W1 are not equal when the woman has non-zero acceleration. (A is incorrect.) (W1 + W2) is not equal to T when the lift has non-zero acceleration. (D is incorrect.) If N = W1, the woman (thus the lift) can be moving at constant velocity. (C is incorrect.) 5 A 1 1 Let be the total mass of the car, the d river and fuel; the fixed retarding force; the change in velocity. Applying Newton's 2nd law of motion to t he two situations: --- (1) m F v vFm t  = ( ) ( ) ( )( ) ( ) 2 2 2 1 2 1 when the car is almost out of fuel --- (2) when the car has a a full load of fuel from (1) and (2), we have 30 50130 0.37 s7000 vFm t vt t m m F = −− = − = = −

DUNMAN HIGH SCHOOL 2024 PHYSICS H2 (YEAR 5) 2 For Internal Use Only 6 C The wires are slightly elastic hence they can be treated as springs. The first wire fixed to the wall will experience the same force F and hence will extend by the same length x. The force F is shared equally by the springs in parallel so each spring experiences half the force and extends half as much, 2 x . Thus, the total extension is 3 22 xxx+= . 7 A Torque = Force multiplied by the perpendicular distance between the line of actions of the two forces. 8 D ( )( ) 9 12 minimum 1.3 10 24 60 W kg s 9.81 m s 2.0 m60 300 kmg h mP g h tt −− = =  = =     9 B The area under the force-extension graph is the total work done to stretch the material. 10 D The net force acting on the stone when it is vertically below the centre of the circle is given by 2T W Mr −= , when T is the tension in the string. 2T W Mr  = + 11 C Gravitational field strength is a vector. It has both direction and magnitude. So C is not true. 12 D The graph shown is an elliptical graph and in simple harmonic motion, the graph of velocity against displacement is elliptical.

DUNMAN HIGH SCHOOL 2024 PHYSICS H2 (YEAR 5) 3 For Internal Use Only 13 C When the plasticine is flattened, the surface area increases leading to an increase in air resistance when oscillating. The new system experiences greater damping than