2024 VJC H1 Prelim P2_Soln

2024 Physics Prelim Exam H1 Paper 2 suggested solutions 1(a) 2 2 2 2 2 1 2 From Fig. 1.1, 1.75 m and = 0.600 s [ 1] 2 2(1.75) (0.600) 9.722 m s 9.72 m s [1]           y y y y s u t gt s t sg t (b) % uncertainty = actual uncertainty/ data point. [1] Hence the larger the data point, the smaller the % uncertainty since the absolute uncertainty is fixed. Hence more reliable. [1] (c) 2 2 2 [1] 0.001 0.006[ 2( )](9.722)1.75 0.600 =0.2 m s [1] 9.7 0.2 m s [1]           y y sg t g s t g g (d) Since sy = ½gt2, plot a graph of sy against t2, where, sy = vertical distance travelled by the sphere, t = time taken to travel sy. The gradient = ½g. [1] Random error is reduced when a best fit line is drawn using all the data points. [1] 2(a) By the principle of conservation of momentum, since there is no external force acting, the total change in momentum of the of ball and wall = 0. [1] Therefore the change in momentum (impulse) of the wall is equal and opposite to the change in momentum of the ball . [1] Therefore, Student A is wrong. (b) Taking values from Fig 2.2, Total momentum before collision = (1.2 x 4) + 0 = 4.8 kg m s-1 [1] Total momentum after collision = (1.6 x 3.6) + (-0.8 x 1.2) = 4.8 kg m s-1 [1]

Since total momentum before collision is equal to the total momentum after collision, momentum is conserved in this collision. [1] (c) Relative speed of approach = 4.0 – 0 = 4.0 m s-1 Relative speed of separation = 1.6 – (-0.8) = 2.4 m s-1 [1] Since relative speed of approach is not equal to relative speed of separation, the collision is inelastic. [1] 3(a) Electric field strength at a point is electric force per unit positive charge at that point. [1] (b)(i)    19 4 14 (2 ) [1 ] 2 1.6 10 7.5 10 2.4 10 N [1 ] F e E          (b)(ii) Time taken for alpha particles to travel 1 m in the horizontal direction, 7 1.0 1.50 10 x x st u   86.67 10 [1 ]s  (b)(iii) Acceleration in the vertical direction, 14 13 2 27 2.4 10 0.3614 10 [1 ]4 4 1.66 10 F Fa msm u           Displacement in vertical-direction during time t,          22 13 81 1 0.3614 10 6.67 10 0.008039 0.0080 [1]2 2s at m The particles will not hit any of the plates as the vertical displacement of the electron is less than 0.0125 m when it is travellling between the two parallel plates. (b)(iv) + V – V Beam

4(a) Magnetic flux density is defined to be the magnetic force acting per unit current and per unit length on a conducting wire [1] placed at right angles to the direction of the magnetic field. [1] (b)(i) Direction of the magnetic flux density is into the plane of the page. [1] (ii) Magnetic force on a charge particle, sinBF Bqv  [1]      73 19