stpm trials 2009 physics answer scheme (johor)

8/8/2019 STPM Trials 2009 Physics Answer Scheme (Johor)

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QuestionNumber1. (0)

(b)(i)

SUGGESTED ANSWERS AND MARKING SCHEMEJOHOR STPM PHYSICS TRIAL EXAMINATION 2009PAPER 2SECTION ASuggested AnswerThe Pr inciple of Conservation of Linear Momentum states that the totallinear momentum of a system is constant ( or conserved) if there is noexternal force acting on the system .co nservation of linear momentum2,Ox 10" x 500 = 1.0 (v ) + 2.0x 10" x 100v= 0.80 m 5.1

(b)(ii) Loss in K.E wooden block=work done against constant or averagefrictional force

2, (0)(b)

3. (o)(i)(ii)

.!.(1.0)(0.8) ' = FR 0.20)2=> FR = 1.6 Nimage is realv =0.25(20) =5.0 em1 1 1 1 1-=-+- = -+ -J U v 20 5.0J=4.0cm

1 1 1- = (n - 1)(-+- )/ T. T2I 2- = (1.65 - 1)-4.0 r

r l = T2 = 5.2cm1 1f= -= -- =25HzT 0.04 50 f iangular frequency : w=2m =157=160 rads"I d - G, 50 20 10- 'amp Itu e , "0- - , = ( )2= . x mIV 157

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(b)

4. (a)(b)

x (x10"20....1 \ _..1 \ ...1 \ ..........U V 0.122.0 ........ ... .. .... ..................................... .. .................... .......................... .

Brittleshow no plastic deformation before it breaksE= FLxA

60xO.24= -....:..:.,:.:...:..::'-'-""""3x104 x8x10 7

=6 .0xI0 IO Nm2

Us

5. (a) A multiplier is a resistor of very high resistance connected in series to ag a l v a n o m e t ~ r

(b) The function of the multiplier is to reduce the incoming current down tothe maxirnu"m current that can be carried by the galvanometer.

(c )

6. (a)

ORThe function of the multiplier is to convert the galvanometer into avoltmeter.

Irsdi - - - {

V=3.0VJ= I

ft d= V = 3.0 = 0.02

r+Rm 30+Rm30 +R. = 3.0 = 150 => R. = 12000.02The multiplier is connected in series to the galvanometer.to reduce the distortion of the outputor to reduce the gain

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CONFIDENTIAL' 3(b)(i) Rf 60Gain 1 A = I +-=I+ - =1+3=4R, 20

(ii) Output, V, = AVm = 4(3 .0) = +12.0V = +9.0V(saturation)

' .. -:. 1( . 0'" ,_.... :. . ....... .12 . . ..-""

. . ,/ ' .'-5 '.. , .:.:r .""11"./ - - " . , - ' " ' - " ~ ' " . /, ) ...: .... ...-.. . -"' .. Til'n..- .:-;:.. \ .""- ./",,;> , .-1 2 ,

7. (a) There is change in magnetic flux-linkage(b) E = BIv=6.0 X 10-5 X 20 X 103 X 7 X 103

=8.4 x 10'V(e) direction of generated e.m.f is from"spa ce shuttle to satellite .8, (a) Combination of 2 lighter (or smaller) nucle i at very high temperature to

produ ce a heavier (or bigger) nucleus accompanied with the release ofa lot of energy.(b)(i) J3C+ lH-+14X, , ,

14X is J4N, ,(ii) Mass defect, MI = (13.003355 + 1.007825)u - 14 .003074u

MI=8.106 x lO"uEnergy released, Q= 8. 106 x 10 -' x 931= 7,55 Me V

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9. (a)

(b)

SECTION BCentripetal force ::: force that causes a body to move in a ci rcle, and itsdirection is always towards the centre of the circle .The statement is false .If the two forces balance each other', the resultant force;:: O. Accordingto Newton's first law of motion, the body will move in a straight line with

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constant velocity. That is the body will not perform circular motion. 1

(e)

(d)(i)

( i)

(e)(i)

(ii)

R

i l lmg

Resultant force towards the centreof circle ;:: mg - Rmv'Hence mg - R;:: --

rFor maximum v, R::: 0v::lrg ;F81 ~ ~ ,9 "I ",,-'Newton's Law of gravitation states that the force between two massesis directly proportional to the product of the masses, and is inverselyproportional to the square of the distance between them.

The gravitational force of attraction is F=

F ; G Mm ., .r

F ; gR' X4R '

9.81x150; 4; 368 NF = mr a/

150

GM = gR2; r = 2R

368 ; 150 x 2 x 6.38 x 10' ", '

G Mmr '

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(iii)

10,(0)

(b)(i)

we'L iI)(iii)

(c)(i)

2"Period T = (iJ= 1.435 x 10' s.

1 1 J 1K . E ~ ~ - m ( ( i J ) 2 2K.E ~ ( 1 5 0 ) ( 2 x 6.3 8x 10 ' ) ' (4.38 x 10-' ) ' 2.3 4 x 10 ' J2

Heat and electric conduction in metals are both caused by the manyfree electrons that moves with high mobility.There are no free electrons in thermal and electric insulators.Thus thermal and electric insulators are poor conductors.Steady state is' achieved when the temperatures at all points along themetal rod are stable and not changing.II 'Temperature gradient is the difference in temperature-per unit lengthalong a conductor. J,..uJI tlx .

(Qll dC/ , kA 1&

Current, f - r - A '\ ' o(;tp l . ..L Kv l ' -Cl.where: 1 is the current in the tlowinl ln the conductor,p is the resistivity of the material conductor,

V is the potential gradient along the conductor.Irate of heat flo w in P=rate of heat flow in Q V 111 .. ;.,=> 4kA(8-0) =kA(100-8) V, l (q ; i, I " I

t'- ) p-.,-1'& : IDO - f-

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(ii)

T moeaturefC

100 ----- ------- -- ---- 1-------- --- ------ -

25 ....,,,.O ~ ~ - - - - - - ~ - - - - - - - - r _21

p Q

Supposition of 2 identical waves travelling in opposite direction.Amplitude of both waves are the same or almost the sameCompare to stationary wave equation y = Asin OJ' kos 2m, l'" = 2nf = 250250f = - - = 39.8 = 40Hz2"2" = 50, l .

2", l = - = O.13m = 13. 0em50distance between 2 neighbouring nodes:;:: A. = !2 = 6.5cm2 2

length

(iii) speed of wave. v=jA=(40)(0.13)=5.2ms-1 X "1\ "", ,-(c)(i)

( l)

(d)(i)

.;vInterference is the superposition of two coherent waves to producepoints of max imum and minimum amplitudefinte nsrty.Two conditions for welldefined interference are:-both waves are coherent and same or almost the same amplitude .Interference at G is constructive interference.Intererence at H is destructive interference.

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(ii) At H, is first minimum where m=1 1(m- )I,)DA (1- )1,)(1.50)(600 xW ' )

y= d = 1.0x 10-3 1'1

12.(a) a) The stationary negative charged particle will move in the direction ofthe gravitational field. 0 eJ "'11

The stationary negative cha rged particle will move oPPosite in directionto an electric field and will not move in a magnetic field. 1

(b)

(e) (i)(ii) _

(d)(i)

Upward electric force =downward gravitational forceeE =mg

charge on Ne ion = 1 .6 x 10.19 C. M 20 x 10-3mass of Ne lon, m=_= 23 3.3x IO -26 kgN, 6.02x 10

Path ofNe+ ions

ORE

Path ofNe+ ions

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CONFIDENTIAL 8(ii)

(iii)

(e)(i)

(ii)

13.(0)(1)

(ii)

(b)

(e)

1 ,-my =eV2V = ~ 2 e v = ,12(1.6 X I0-" )(1400) =2.2x l0 ' ms -'

m V 9.1 x lO-31 'electric force = magnetic forceeE =Bev

8==6 .2 x l0' =2.8 x l0-' Tv 2.2xl0 '

Charge doubled, speed v increased by J2 t imes.Magnetic force> electric force, ions deflected from original path.

The de Broglie's relationship gives the value of the wavelength )_hrelated to a particle of linear momentum p in the equation A. = -p

where h is the Planck constantThe wave-particle duality refers to the wave nature of a particle undercertain specific conditions and the converse is also true

.!. mY' = 50 ( 1.60 x. W " )2mv = ~ 2 x 5 0 ( 1 l " ) m

de Broglie wavelength A. = hmv6.63xl 0-" = 1.74 X 10.10 m ;mv me =9 .11 x 10.31 kg

Continuous spectrum is produced when fast electrons from the cathodeare decelerated on collision with the target . The decrease in energy ofthe decelerated electrons is rad iated as photons in the continuousspectrum.Characteristic X-ray is produced when a vacancy in the inner shell(e.g. K-shell) of the target atom is filled by an electron from a highershell.

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The difference in energy of the electron is radiated as a characteristic 2X-ray photon.

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(d)

(e)

(f)

14. (a)

(b)(I)

Intensityline spectrum

continuous spectrum

wavelength

When an electron collides with a target atom, the electron willdecelerateand is stopped. The loss of aU the kinetic energy E of the electron in asing le collision with the atom means that the X- ray emitted has

. h f hemaxImum paton energy 0 - -heeV= -

..t,Nn

A . = helIua 20xlO J x1.60xlO -'9

= 6 .22 x 10"'m

A""

Half-life : the time taken for the number of radioactive atoms in asample to decay to half of its initial number.

decay constant =dNdlN

Ra -----+ Rn + ; He(ii) Mass defect /:, m = 226 .025402u - (222.017570 + 4.002603)u

= 0.005229 uTotal K.E =0.005229 x 931= 4 .88 MeV

(c)(I) 4 a + 9Se --.to 12 C + IX 0

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stpm trials 2009 physics answer scheme (johor)

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