PHYSICS. Units 3 & 4 Written examination. (TSSM s 2008 trial exam updated for the current study design) SOLUTIONS. TSSM 2017 Page 1 of 1

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1 PHYSICS Units 3 & 4 Written examination (TSSM s 008 trial exam updated for the current study design) SOLUTIONS TSSM 017 Page 1 of 1

2 SECTION A - Multiple Choice (1 mark each) Question 1 Answer: D Magnetic, electric and gravitational field lines never cross. Question Answer: C Using the right hand rule the force depends on the direction of the field and the direction of the current Question 3 Answer: A 1 Vq mv V V 91V 8 Question 4 Answer: B mv r Bq B mv rq B B T 8 TSSM 017 Page of

3 Question 5 Answer: A F qvb F F N Question 6 Answer: A Question 7 Answer: B ( ) kn Question 8 Answer: A ( ) TSSM 017 Page 3 of 3

4 Question 9 Answer: A The Michelson Morley experiment was designed to measure the speed the Earth moves through the aether Question 10 Answer: B N p VP 0 N V 1 S S N 1 So S V s VP 40 = 1 V AC RMS N 0 P Question 11 Answer: D When a sound wave is moving towards an observer each wave crest is emitted closer to the observer hence takes less time, this leads to a perceived increased frequency. Question 1 Answer: B An electromagnetic wave can be created by accelerating charges. TSSM 017 Page 4 of 4

5 Question 13 Answer: C Question 14 Answer: D Hz Question 15 Answer: C An electron is a particle. In order to form a standing wave around a nucleus it has a number of wavelengths equivalent to the circumference of the nucleus. Question 16 Answer: D The uncertainty principle says that we cannot measure the position and the momentum of a particle with absolute precision. Hence if we cannot measure position or momentum with absolute precision in the present its impossible to predict the future. Question 17 Answer: D Laser light is in phase, monochromatic and narrow TSSM 017 Page 5 of 5

6 Question 18 Answer: C Sound waves due to their longitudinal nature cannot be polarized. Question 19 Answer: A Systematic errors are instrumental errors Question 0 Answer: B The independent variable is changed within an experiment to lead to a change that can be measured in the dependent variable. SECTION B Short Answer Question 1 (3 mark) N C -1 vertical Vector addition: N C -1 horizontal N C -1 TSSM 017 Page 6 of 6

7 N S Question (6 marks) a. V b. N marks marks c. N C -1 marks Question 3 (4 marks) a. S N Field lines must be continuous, starting from a North pole and finishing at a South pole. marks b. Answer: D Use RH Grip rule for the wire marks TSSM 017 Page 7 of 7

8 Question 4 (9 marks) a. g = GM 70 r ( ) Nkg 6 marks b days = = s c. Acceleration of Mars around Sun 4 r = T = 7 (5.94x10 ) = GM g m/ s.55 M r M (.810 ) = kg Hence mass of Sun is kg d. T s 3 GMT r = = 4 1 = So r.0410 m km Hence distance above planet surface: km km m 1 mark TSSM 017 Page 8 of 8

9 Question 5 (8 marks) a. Vertical component of velocity = 50 sin 60 = 43.3 m/s In vertical direction, v u at t t 4.4 s Hence total time of flight t s b. Horizontal component of velocity = 50 cos 60 = 5 m/ s In horizontal direction, d vt d d 1m c. Acceleration = g = 9.8 m/s down d. Air resistance would reduce the range of the golf ball. marks marks 1 mark Question 6 (9 marks) a. Given that the collision is isolated, we can assume momentum is conserved Total momentum before the collision = Total momentum after the collision If East is assigned as positive momentum: v v = 1 m/ s West b. Change in momentum of blue ball = Final Momentum Initial Momentum = = +0.1 kg m/ s Ft = Change in momentum F F 0. 8N East Average force exerted by blue ball on red ball is 0.8 N East. c. The collision is inelastic. TSSM 017 Page 9 of 9

10 Total Kinetic Energy before collision = J Total Kinetic Energy after collision = = 0.105J Since Total Kinetic Energy before collision > Total Kinetic Energy after collision the collision is inelastic. Question 7 () 0 a. 0 km/ hr = m/s 3.6 = 5.6 m/s mv b. Net Force = r = 3.5 = N towards the centre 1 mark marks Question 8 (4 marks) a. F m g m g 1. N a b 6 Newton s First Law marks b. 0 N All of three books free fall. There is no force acting between the books. marks TSSM 017 Page 10 of 10

11 Question 9 (7 marks) 1 d a. Time = = = s = 18 hrs 1 mins 35.6 s. s Hence Daisy s watch would read 6:1:36 am. marks b. 1 and v 1 c Substitute v with 0.3c and solve for γ = Hence Donald would measure a time of s. Hence Donald s watch would read 5::17 am. = s or 17 hours mins L o 7 c. Length = = = 6.68 m marks Question 10 (5 marks) a. F nbil n n 90turns marks b. FORCE on SIDE AB FORCE on SIDE BC CURRENT in SIDE AB No change Decreased (zero at vertical) Increased (zero at horizontal) TSSM 017 Page 11 of 11

12 Question 11 (6 marks) a. (Wb).8 x Time (s) max BA Wb marks b. emf (V) Time (s) The emf is the negative gradient function of the flux curve, due to emf n t marks TSSM 017 Page 1 of 1

13 c. Answer: C Use emf n t n 0.04 n = 50 4 marks Question 1 (10 marks) a. Clockwise. Consider a positive charge at A. If the turbine spins clockwise, at the instant shown, the positive charge will be rising. The RH slap rule shows that the charge will be pushed (by an induced force) from A to B as required. (Note: The pushing of the charge is the induced current) b. The slip rings are permanently connected to opposite sides of the coil, so as the induced current alternates in direction, the slip rings carry this alternating current to the external circuit. marks c. This setup is a generator, as the coil is rotating within a magnetic field. An alternator is similar, but the magnet rotates inside stationary coils, where current is induced. d. A transformer requires alternating current because it relies on the transfer of constantly changing flux (which is created in the primary coil by the alternating input current). This flux is carried by a central iron core and induces voltage and current in the secondary circuit. DC current will not work because it will only lead to a constant magnetic field and thus no change in flux. marks TSSM 017 Page 13 of 13

14 Question 13 (9 marks) a. V V peak peak V marks b. I I I RMS RMS RMS P V RMS A c. I I V V V peak peak peak peak drop drop drop IR I 5V RMS 17.7 A marks marks d. An increase in current in the shack will lead to an increase in the current in the cables. This will lead to a larger voltage drop in the cables and thus a smaller V PRIM. When stepped down, this will make V SEC less than 110 V. Question 14 (4 marks) Source of Light Spectrum (Continuous / Discrete) Nature of Phase (Coherent / Incoherent) Electron behaviour (Thermal motion / Quantised energy level) LASER Discrete Coherent Quantised energy level Candle Continuous Incoherent Thermal motion Metal Vapour Lamp Discrete Incoherent Quantised energy level Incandescent Globe Continuous Incoherent Thermal motion TSSM 017 Page 14 of 14

15 Question 15 (1) a. marks b. Independent = wavelength of laser light Dependent = path difference marks c. Obtain the red laser and the double slit. Set the double slit up at a set distance from a screen Shine the laser light through the double slit and observe the interference pattern formed on the screen. marks d. nm e. Systematic laser Random measurement marks marks f. ( ) nm = 1.5λ m Hz Question 16 (6 marks) 34 h a. p kgms marks b. p mke kgms 1 marks TSSM 017 Page 15 of 15

16 c. V hf hf f o o Hz f o marks Question 17 (4 marks) a. Check each wavelength to determine its Energy value: 776 nm = 1.6 ev (No corresponding energy gap) 591 nm =.1 ev (drop from 4 to 3) 185 nm = 6.7 ev (drop from 3 to 1) 6 = 5.5 ev (No corresponding energy gap) hc E marks b. Electrons will only exist at energy levels which correspond to standing waves (the wavelength for this is derived from their de Broglie wavelength). From the energy level diagram, it appears that the 4.5 ev (76 nm) level is not viable for this particular atom. marks TSSM 017 Page 16 of 16