Answer Scheme Physics Spm 2011

ANSWER SCHEME PHYSICS SPM 2011 KERTAS 2 Section A 1 (a) Alternating current (b)(i) P, Q (ii) ST is greater than PQ (iii) Acceleration 2 (a)

Step down transformer

(b) (i)

(ii) P = IV 24 = (I)12 I=2A (c) Diode 3 (a) The time taken for the activity of that radioisotope to fall to half its initial value. (b) To be more stable (c) (i) T 1/2 = 8 days 4 T ½ = 32 days Iodine-131 has to go through 4 times T ½ 200 g

T 1/2

100 g

175 g

150 g

100 g

T 1/2

50 g

T 1/2

25 g

187.5 g

T 1/2 12.5g

After 32 days, the mass of the iodine-131 that still active is 12.5 g. (ii)

Mass (g)

200

100 50 25 12.5 8 16 24

32

Time (days)

Has decayed Still active

4 (a) (i) (ii) (iii) (b)

M M is forced to oscillate at its natural frequency Resonance F = 1/T 2 = 1/T T = 0.5 s

(c) Displacement

T1

T2

Time

5 (a) (b) (i) (ii) (iii) (iv) (c)

(d) 6 (a) (b)(i) (ii) (iii) (c)

air pressure The reading of Bourdon gauge in Diagram 5.2 is higher than that in Diagram 5.1 The reading og the thermometer in Diagram 5.2 is higher than that in Diagram 5.1 As the heat increases, the temperature increases As the temperature increases, the air pressure in flask increases – when the molecules received heat, it will move faster. -This will lead to an increase of kinetic energy of the air molecules - The collision between the molecules become more often Pressure law

parallel Number of bulbs in Diagram 6.1 is more than that in Diagram 6.2 The reading of the ammeter in Diagram 6.1 is higher than that in Diagram 6.2 As the number of bulbs increases, the reading of the ammeter increases In Diagram 6.1, the greater number of bulbs in parallel produces a lower effective resistance (R) and hence, a larger current. (d) A greater number of bulbs in parallel produces a lower effective resistance and allows more current to flow in circuit. (e)(i) P and Q (ii) Vtot = VP = VQ, across P and Q is lower than that across R and S.

7 (a) combination of electronic devices with multiple inputs but only one output (b)(i) Transmitter Sensor Output X Pemancar Pengesan Output X 0 0 0 0 1 0 1 0 0 1 1 1 (ii) (iii)

AND gate

(c)(i) -smaller mass -reduce inertia (ii) -higher power -motor rotates faster 8 (a)(i)

(ii)

(iii) Total internal reflection (b)

(c)(i) – A longer focal length - Gives a higher magnification (ii) – A lens with a bigger diameter - More light can be refracted by lens/brighter image (d) R

Section B

9 (a) To freeze the motion (b)(i) -Distance between two consecutive images in Diagram 9.2 larger. -The depth of nail in Diagram 9.2 larger (ii) Distance between two consecutive images larger, velocity larger (iii) The depth of nail larger, force larger (iv) When velocity is larger, the force larger (c) - the taekwondo exponent’s hand moves very fast - The hand stops very quickly - Time taken to smash the wooden block is small - The change in momentum is great - The impulsive force is great (d)(i) -small mass -move faster (ii) -aerodynamic -less air resistance (iii) -larger elasticity bow string -higher elastic potential energy (iv) -strong bow -not easily break (v) -position of the aiming arrow must above the level of the centre of the target board 10 (a)(i) a temporary magnet / a conductor which becomes magnet when current flows (ii) -number of turns in Diagram 10.1 is equal to the number of truns in Diagram 10.2 -reading of ammeter in Diagram 10.2 bigger

-number of iron nails attached in Diagram 10.2 is more -the number of iron nails attached increases as the reading of ammeter increases -the electric current increases, the strength of electromagnet increases (b)(i) -easy to magnetize and demagnetize (ii) -when current flow, soft iron core is magnetized -iron armature is attracted -the secondary circuit is switched on (c) -increases the number of turns of the coil -increases the strength of electromagnet -bigger gong -increase the vibration -higher elasticity of springy steel strip -increases the hitting force -U-shape soft iron core -increases the strength of electromagnet -thick wire -low resistance / larger current Section C 11 (a)(i) pressure applied to a fluid is transmitted equally in all directions throughout the fluid (ii) -the force applied to the small piston produce pressure -pressure transmitted equally throughout the liquid -F2 is produced when pressure acts on A2 F2 = PA2 -A2 > A1 / Ratio A2:A1 is greater than 1 and F2 > F1 (b) -incompressable brake fluid -pressure can be transmitted through the brake fluid equally to all direction -high boiling point -not easy to evaporate -high spring constant -can withstand huge force -low ratio -larger force exerted on the piston -choose L -incompressable brake fluid, high boiling point, high spring constant and the ratio of cross sectional area of piston in the master cylinder to the brake drum is low. (c)(i) Correct substitution

(ii) State the correct formula Force = Pressure x Area = 25 x 6 = 150 N 12 (a)(i) Isotope of an element which is not stable (ii) M – Alpha N - Gamma (iii) Alpha – Highest ionizing power Gamma – lowest ionizing power (b) - liquid -easy to absorb by the plants -medium half-life -can be detected in a suitable period -Beta ray -less dangerous -GM tube as detector -can detect ray easily -Choose Y -liquid state, medium half-life, beta ray and GM tube as a detector (c)(i) Show the correct substitution Mass defect = (235.04392 + 1.00867) – [91.92611 + 140.91441 + 3(1.00867))] = 0.18606 u (ii) Correct conversion 0.18606 x 1.66 x 10-27 = 3.088596 x 10-28 E = mc2 = (3.088596 x 10-28)(3 x 108)2 = 2.7797 x 10-11 J