PHYSICS Unit 3 Trial Examination

Transcription

1 STAV Publishing Pty Ltd 005 PHYSICS Unit 3 Trial Examinatin SOLUTIONS BOOK Published by STAV Publishing Pty Ltd. STAV Huse, 5 Munr Street, Cburg VIC 3058 Australia. Phne: Fax: stav@stav.vic.edu.au Website: STAV Publishing Pty Ltd March 005 ABN All rights reserved. Except under the cnditins described in the Cpyright Act 968 f Australia and subsequent amendments, n part f this publicatin may be reprinted, reprduced r utilised in any frm r by any electrnic, mechanical, r ther means, nw knwn r hereafter invented, including phtcpying and recrding, r in any ther infrmatin strage r retrieval system, withut permissin in writing frm the publisher. SEMESTER

2 STAV Publishing Pty Ltd 005 Physics Unit 3 Slutins Physics Unit Slutins Area f study Mtin in ne and tw dimensins Q Answer Slutin 3. s Vertically: u 0 a 9.8 s 5 t? 3 m s - Vertically: u 0 a 9.8 s 5 v? s ut + ½ at ½ 9.8 t t t (5 4.9) t 3.6 v u + as v v v (999.6) 3.6 The speed is fund vectrially using Pythagras. speed speed 4.6 speed θ tanθ θ θ tan B At Tp GPE mgh mg 5 5mg At. m frm bttm GPE. mg Kinetic energy 5 mg. mg.8 mg GPE KE. mg.8 mg 4 r : kg m s - p mv Reprduced under licence by STAV Publishing Pty Ltd, 005

3 STAV Publishing Pty Ltd Physics Unit 3 Slutins 6 In rder fr the tw vehicles t cme t a dead stp after the cllisin they must have equal and ppsite mmentum befre the cllisin u car u car u car 36.6 m s - but 50 km/h 3.89 m s - Yes the car was SPEEDING i.e. exceeding the speed limit! N Van: u 5 v 0 t 0.0 a? v u +at a 0. a 0. 5 a ms F ma Magnitude nly, s F 4500 N OR p i p f 0 p 900 F av t F av Magnitude nly, s F 4500 N 8 The driver s inertia keeps him mving in a straight line. As the car turns t the right the driver will feel he is mving utwards relative t the car. His feeling f a frce pushing him ut is in fact his reactin frce t the frce frm the car pushing him arund the curve. 9 9 m s - F c v mv 0.30 mg r 0.30 rg v S 87 E r 93 T v pa 600 km/h unknwn directin v ag km/h Nrth v pg unknwn speed East sinθ 600 θ sin bearing True r Suth 86. East θ v pg 00 N m - k the gradient f the graph k rise run Reprduced under licence by STAV Publishing Pty Ltd, 005

4 STAV Publishing Pty Ltd Physics Unit 3 Slutins 36 J EPE KE EPE ½ kx ½ J 3 D Gm gravity g r g α radius An altitude f r m is a radius f 3 r m The gravitatinal field will therefre be reduced by a factr f 3 9 This is g m, answer D J The increase in KE decrease in GPE. The change in GPE per kg is given by the area under the field vs altitude graph. Area 35 squares J kg - Change in KE is then.75 6 J kg - 50 kg KE J 5 5 N Read frm the graph that at the surface f Mars g m 3.6 N kg - W mg s 3.6 At r m abve the surface f Mars g 0. 4 N kg - 9 And r 3 r m 4π r 4π g 0.4 T T 6 4π T T 3868 s 6 Reprduced under licence by STAV Publishing Pty Ltd, 005

5 STAV Publishing Pty Ltd Physics Unit 3 Slutins Area f study Electrnics and phtnics + V +9 V +6 V +3 V X V Ω 0 Ω 0 Ω switch (clsed) X The tw 0 Ω resistrs in parallel are equivalent t a single Ω resistr, the ptential difference will be 6 V acrss the single Ω resistr and 6 V acrss the parallel cmbinatin. + V +9 V +6 V +3 V X V Ω 0 Ω 0 Ω switch (pen) X The switch is pen, s n current flws in the circuit s there is n ptential difference acrss the resistrs. The whle V drps acrss the switch. Reprduced under licence by STAV Publishing Pty Ltd, 005

6 STAV Publishing Pty Ltd Physics Unit 3 Slutins 3 3. V lux R 0 Ω frm the graph V ut r 4 The magnitude f the slpe f the amplifier characteristic gives the gain f the amplifier. 6 gain Inverting means that a small psitive change in the input vltage results in a large negative change in the utput vltage. Cnversely a small negative change in the input vltage results in a large psitive change in the utput vltage. This is indicated by the negative gradient f the amplifier characteristic. 6 V ut (V) time 7 Amplificatin shuld NOT change the frequency f the input signal mv Bias is the vltage value at the centre f the linear sectin f the characteristic graph 0.3 mv. T zer bias this amplifier, 0.3 mv needs t be taken ff the input signal. Reprduced under licence by STAV Publishing Pty Ltd, 005

7 STAV Publishing Pty Ltd Physics Unit 3 Slutins 9 4 µa Acrss R b : V b I b R b ( ) I b 0 3 I b 5.3 (0 3 ) I b.9-5 I b 4.09 µa.7 V I c 50 I b I c I c A Acrss R c : V c I c R c V c V c 4.34 V ut Detailed study Einstein s special relativity The speed f light is s fast that attempting t take visual bservatins n Earth wuld give a virtually instantaneus result. T measure the speed f light using relatively shrt terrestrial distances requires extremely accurate and fast reacting clcks nt available in Galile s time..3 8 m s - The difference between the Earth s psitin after 6 mnths is the diameter f the rbit ( 50 9 m). The time difference is 60 s. v The speed f the ball is much less than the speed f light s n time dilatin will be bservable. The times fr the tw bservers will be the same. 4 /7 r :7 Steve sees the speed f the ball as 5 m s -. Sphie sees the ball s speed as m s - rati years t d v years Reprduced under licence by STAV Publishing Pty Ltd, 005

8 STAV Publishing Pty Ltd Physics Unit 3 Slutins 6 4. years t t t v c (0.9c) c t γ light years l l γ c l l 0 γ γ γ 0 v c c γ c 9 In special relativity, time is relative and the maximum pssible velcity is abslute, the speed f light c. This is basically the ppsite f the classical physics mdel. Light was thught t be a wave. All waves s far bserved needed a medium t travel thrugh. Fr light this hypthetical medium was called the aether. The cnsequence f the M-M experiment was that there was n experimental evidence fr the existence f the hypthesized aether placing the wave thery f light in questin. Many scientists at the time cntinued t search fr evidence f the aether r t find fault with the M-M experiment..5 - J E γ m c E E v c 0. E.55 m c ( 3.0 ) Reprduced under licence by STAV Publishing Pty Ltd, 005

9 STAV Publishing Pty Ltd Physics Unit 3 Slutins Detailed study Investigating materials and their use in structures C Bth cnditins are necessary fr stability. A A member under tensin culd be replaced with a rpe. The hrizntal member seems t be the nly ne that wuld remain in tensin if replaced with a rpe. 3 Material Rubber Steel Glass Graph C A B Glass is brittle B Steel is ductile A Rubber is neither C 4 Descriptin Elastic regin Ductile failure Plastic regin Maximum stress Elastic limit Pint r Regin D C E B A 5 The large plastic regin n the graph indicates that the material is ductile. 6 Ductile It will stretch a small amunt until the elastic limit is reached, then the stretching will increase rapidly with the applicatin f little further stress until the material fails. OR Ductile materials will becme plastic under large lads. Brittle This material will stretch a small amunt then fracture with n ductile regin. OR Brittle materials have n yield pint and fail under lad at their ultimate tensile strength kg sin W m g W 450 W 450 sin N 450 W N m - 3 F πd π ( 3 ) 7 σ A 4 Reprduced under licence by STAV Publishing Pty Ltd, 005

10 STAV Publishing Pty Ltd 005 Physics Unit 3 Slutins m σ σl σl Y L ε L Y L Detailed study 3 Further electrnics Silicn Silicn dides typically have a switch-n vltage f V while germanium dides require 0.3 V t switch-n. B The utput will be half-wave rectified. This is because the dide nly allws the current flwing t the right t pass thrugh it s 3 6 τ RC s time (ms) -.0 The dide will use V which decreases the peak vltage t.3.4 vlts. The capacitr will smth the half wave rectified vltage t a virtually flat line due t the lng time cnstant (3.3 s) cmpared t the perid f the input signal (0.0 s). The utput signal will appear as a flat line at ~.3.4 V with virtually NO ripple vltage. Reprduced under licence by STAV Publishing Pty Ltd, 005

11 STAV Publishing Pty Ltd 005 Physics Unit 3 Slutins 5 P V AC R lad Output Vltage Q 6 60 turns V V N N N N 7 C Dide Bridge causes full-wave rectificatin graph C 8 By placing a large capacitr in parallel acrss the resistr. 9 Situatin Psitin Charging the capacitr X Discharging the capacitr Y 5.0 s τ R C 3 6 τ 50 0 τ.0 s The capacitr is fully charged after ~ 5 time cnstants. 5τ 5 s Reprduced under licence by STAV Publishing Pty Ltd, 005

12 STAV Publishing Pty Ltd 005 Physics Unit 3 Slutins Vltage (V) time (s) Discharge resistr 50 kω cmpared t 50 kω fr charging. τ discharge 5 x τ charge 5 x 5 s fully discharged after 5 s Vltage (V) time (s) Reprduced under licence by STAV Publishing Pty Ltd, 005