Section A [40 marks]

Section A [40 marks]

Answer all questions from this section.

1(a)Define a vector quantity.

(b)The diagram below shows a 5.0 kg street light suspended by two cables.

Calculate the tension in each of the cables.

(

or 25 N

(

or 38 N

2(a)StState the conditions for equilibrium of a rigid body.

Nett force acting on an object must be zero (or resultant forces zero)/ forces form a closed polygon

Nett torque about any axis must be zero (or the total moments about any axis is zero)

(b)The diagram below shows a 20.0 kg mass hanging at the end of a horizontal beam. The beam of length ( and negligible mass is hinged on the wall at point A. A cable at an angle of 30( to the horizontal is used to support the load.

(i)Calculate the tension in the cable.

Torque about perpendicular axis through A:

or 390 N

(ii)Determine the reaction on the beam by the wall.

To determine the reaction: let X and Y be the horizontal and vertical forces acting at A.

(

or

R=

= 339.8 N or 340 N 3A lens of refractive index 1.52 is coated with a layer of transparent material with refractive index 1.38. The thickness of the coating material is such that the reflection of light at wavelength 400 nm can be eliminated.

(a)Determine the condition for interference to occur.

Phase difference of ray 1 & 2 ( 0 / coherent

( Optical path difference ( 2nct

Constructive interference ( ( 2nct ) = m(

Or Destructive interference (( 2nct ) ( (

(b)

Calculate the minimum thickness of the coating material. [1]

(

(

( 72.5 nm

[1]

4(a)State the differences between gaseous, liquid and solid phases in terms of their atomic arrangements and movements.

Atomic arrangement:

Gas distance between molecules very large/ not packed.

Liquid distance between molecules very much closer than molecule in gas/packed.

Solid distance between atoms are close to each other/very packed

orrg > r( > rs or appropriate diagrams[1]

Movement

gas freely ( and randomly)

liquid translational/ random

solid oscillate/vibrate about their respective equilibrium position

(b)The variation of repulsive force Frep with distance r between two atoms can be represented by the equation

Frep ( ,

where a and n are positive constants.

(i)Sketch the graph of Frep against r.

(ii)Based on the graph in (b)(i), explain why a gas can be compressed but it is almost impossible for a solid.

For gas r is very large, Frep / gradient is small therefore easy to compress

For solid r is small, Frep / gradient is very large therefore difficult to compress

5The diagram below shows two point charges (1.2 (C and +1.0 (C separated at a distance of 0.6 m. Point O is the midpoint of the two charges. Calculate the electric potential at point P which is 1.2 m vertically above O.

r = Pq1 ( Pq2 (

Potential at P due to q1 ( (1.2 (C

V1 (

(

( ( (8.71/8.731) ( 103 V

Potential at P due to q2 ( +1.0 (C

V2(

(

( (7.26/7.276) ( 103 V

The total potential at P ( ( 1.455 ( 103 V/ -1 x 103 V 6(a)What is meant by eddy current?

Eddy current is an induced current on a metal plate/conductor due to its motion in magnetic field or due to changing of magnetic flux.

The direction of the eddy current is such that the magnetic field they create

oppose the flux change producing them.

(b)How is power loss in a transformer measured?

The difference between input power and output power.

(c)How is power loss due to eddy current reduced?

To reduce this current, the iron core is made laminated/comb-like plate(that is build

in thin layers separated by non conducting materials such as metal oxide.)

This increases resistances to the path of eddy current/ confined the

eddy current to individual layers.

7

The work function for Cesium is 2.14 eV. Calculate the maximum kinetic energy of photoelectrons emitted from Cesium surface when illuminated by light of wavelength 565 nm.

Incident photon energy ( hf

(

(

( 2.20 eV / 3.52 x 10-19 J

so maximum kinetic energy( Incident photon energy ( work function

( 2.20 2.14 ( 0.06 eV or 0.0544 eV or 9.6 x 10-21 or 8.7 x 10-21 or 1.0 x 10-20 J8A radioisotope tracer was injected into a human body. After 24 hours, the activity of radioisotope has reduced to 6% of its initial activity. Calculate the half-life of the radioisotope.

A ( A0 or

0.06 A0 ( A0

( ( 0.1172 hrs(1

( 5.91 hrs or 6 hrs

Section B [60 marks]

Answer any four questions from this section.

9(a)Describe briefly a projectile motion. [2 marks]

An object moving in both x and y/horizontal and vertical directions simultaneously / at the same time/together or describing or draw diagram the parabolic path of motion

under the influence of gravity/ constant acceleration.

(b)A marble of mass 30 g rolls off the edge of a table at height 2.0 m and strikes the floor at a horizontal distance 2.8 m from the edge of the table.

(i)Calculate the time taken by the marble to reach the floor.[2 marks]

From

For vertical component:

or

or t =

=

= 0.64 s

(ii)Determine the speed of the marble just before it falls.[2 marks]

Let equal the speed of the marble.

(

or ux =

=

= 4.38 m s(1 or

(iii)Calculate the magnitude and direction of the velocity of the marble just before it reaches the floor.[5 marks]

From

Take vertical component

vy

= ( ()6.28 m s(1 or 6.3 m s-1

Magnitude:

( 7.66 m s(1 or 7.7 m s-1

Direction:

(55(/ 55 (below) horizontal/ shown in diagram

(iv)Determine the average power of the marble.[4 marks]

Energy: U ( mgh or mvy 2

( 0.03 ( 9.81 ( 2

( 0.59 J or 0.6 J

Power: W (

or

10(a)State the characteristics of electromagnetic waves.[2 marks]

(

andare perpendicular to the directions of propagation of the wave.

(

andare perpendicular to each other.

( Electromagnetic wave requires no medium.

( The wave travels in vacuum with definite and unchanging speed/with speed of light.

Transverse wave Can be polarised

( There is a definite ratio between the magnitude ofand, i.e. E ( cB

(b)The displacement y at distance x and time t of a sound wave propagating in air can be represented by

y ( 7.5 ( 10(4 sin (315t 1.05x),

where x and y are in metres and t is in seconds.

(i)Sketch, on the same axes, a graph of y against x at times t ( 0 and t ( where T is the period of the wave.[2 marks]

y ( 7.5 ( 10(4 sin (315t 1.05x)

(ii)Determine the velocity and the frequency of the wave. [4 marks]

Velocity

= 300 m s(1

( ( 2(f

(iii)Calculate the phase difference of a point 2.0 m from the origin. [3 marks]

/ or 5.99 m

(c)Describe the principle of Doppler radar used by the police to determine the speed of an automobile.

[4 marks]

( Police sent out a (micro)wave (of frequency f towards a speeding/moving automobile)

( The automobile reflected the wave (of frequency f1)

( The police detected/measure the reflected wave

( From Dopplers shift (f and f2)/change in frequencies, the speed of the moving automobile can be determined or the formula for Dopplers effect, i.e. or [ As long as Dopplers equation is given] 11(a)(i)What is meant by work done in an isolated gas system?[1 mark]

Work done in a system of isolated gas undergoing a change is defined as

the product of the pressure and the change in volume during the process.

or W ( pV or W ( ; p = pressure and V= volume

(ii)Differentiate between internal energy and thermal energy of a gas system.

[2 marks]

Internal energy=/kinetic energy + Potential energy

Thermal energy The portion of internal energy that changes with temperature.

(iii)State the first law of thermodynamics and the meaning of each symbol used.

[2 marks]

Q (

U + W

Q ( Heat gain (+) or loss (()

U ( Increase or decrease in internal energy

W ( Work done by the system (+) or on the system (-)

(b)An isolated system of 3.0 moles of ideal gas is initially at pressure and volume V1. It is then allowed to expand at a constant temperature of T ( 350 K to a new pressure and a new volume V2 which is twice its initial volume V1.

(i)Sketch the p-V diagram to show the expansion process and shade the region representing the work done during the process. [2 marks]

(ii)Calculate the work done during the process. [3 marks]

Work (

for ideal gas pV ( nRT

(W ( constant T ( nRT

( (350 )

( 6.048 ( 103 J

= 6048 J / 6.0 x 103 J

(c) The diagram below shows a window glass insulation of a house which consists of two glass panels separated by a layer of air.

The area of the window is 2.0 m ( 1.5 m. The outer glass thickness is 5.0 mm, the inner glass thickness is 3.0 mm and the air layer thickness is 3.0 cm. If the temperature outside the house is 45 C and the temperature inside the house is kept at 20 C, calculate the energy per hour that is prevented from entering the window.[5 marks]

[Thermal conductivity of glass ( 0.84 W m(1 K(1,

thermal conductivity of air ( 0.023 W m(1 K(1.]

The rate of heat flow by conduction

and the rate of heat flow at each interface is constant.

With insulation, the rate of flow through the window is

In l hr Qi ( (57.1 ( 3600)

( 2.1( 105 J or J h-1Conducted through the window

Without insulation

( 7.875 ( 103 J s(1

in l hr Qn ( 2.835 ( 107 JConducted through the window

( Energy prevented to go through

(2.84 ( 107 ( 2.1 ( 105) ( 2.82 ( 107 J 12(a)State two functions of the dielectric in a capacitor.[2 marks]

To reduce the potential difference across the plates

(To solve the problem of maintaining two large metal sheets at very small separation.

(To increase the storage of charges./ capacitance

(Can tolerate stronger electric field without breakdown.

(b)Two pure capacitors with capacitance C1 = 5.0 (F and C2 = 10.0 (F are connected in series to a 10.0 V battery.

(i)Derive an expression for the effective capacitance CT of the circuit and calculate the value of CT.[4 marks]

VT ( V1 + V2

CV ( Q

or

( CT (

CT (

(ii)Calculate the total energy stored in the circuit.[2 marks]

Energy stored U ( or or

(

( 166.5 ( 10(6 J

( 1.7 ( 10(4 J or 1.65( 10(4 J

(c)The battery in (b) is replaced by an alternating current supply of maximum voltage 10 V and frequency 120 Hz.

(i)Calculate the reactance of the combined capacitor. [2 marks]

( 10 V

f ( 120 Hz

Reactance is inversely proportional to the frequency of the

alternating current supply.

XC (

( 398 ( or 402 ( or 400 (

(ii)Calculate the maximum current in the circuit. Comment on the phase of the current with reference to the voltage supplied. [3 marks]

The current is (

(

( 0.025 A

The current leads the voltage/ voltage lags current by 90 or

(iii)Describe briefly the behaviour of the energy stored in the combined capacitor during a cycle of the alternating current supply. [2 marks]

13(a)State de Broglie hypothesis and give the relationship between momentum p and wavelength ( of a particle.[2 marks]

de Broglie hypothesis state ( that since light displays particle-like behaviour,

perhaps) particle displays wave-like behaviour.

The relationship according to de Broglie

( = , h = Plancks constant

(b)In an electron diffraction experiment, an electron beam which is accelerated on a potential difference is incident normally on a very thin gold film. Several circular diffraction rings are seen on a photographic film.

(i)If the voltage at the anode is increased, what happens to the circular rings?

[1 mark]

Circular rings becomes narrower/ smaller.

(ii)If a particular ring of radius R is chosen and different values of accelerating voltage V are recorded, sketch a graph of R against Deduce that the experiment is in agreement with the de Broglie hypothesis.[6 marks]

.

.

(c)(i)A 60 kg marathon runner runs at a speed of 5.1 m s(1. Calculate the de Broglie wavelength of the marathon runner.[2 marks]

p ( mv

( 60 ( 5.1 = 3.06 ( 102 kg m s(1

( (

(

( 2.2

(ii)Explain briefly the production of continuous and characteristic X-rays.[4 marks]

Continuous X-rays

Bombardment of energetic electron to the target

Deceleration of electron causes the emission of X-rays

Characteristic X-rays

Energetic electron knocking out electron of inner shell

Electron from outer shell fill in the vacancy (in inner shell causes

the emission of X-rays) 14(a)(i)Define nucleon number and proton number. [1 mark]

Nucleon number is the total number of proton and neutron in a nucleus.

Proton number is number of proton in a nucleus.

(ii)What are isotopes?[1 mark]

Isotopes are atoms of an element which have nuclei with the

same number of protons but different number of neutrons.

or same chemical properties but different physical properties

(b)The diagram below shows a schematic model of a mass spectrometer. An ion enters the velocity selector with electric field E and magnetic field B1. The velocity of the ion of charge q at slit S is v. The ion then enters the region of magnetic field B2 where it is deflected in a circular path of radius r.

(i)Express v in terms of E and B1.[1 mark]

qE ( qvB1

v (

(ii)Derive an expression for the mass m of an ion in terms of E, B1, B2, r and q.

[2 marks]

Centripetal force ( Force due to magnetic field

or

(iii)If B1 ( B2 ( 0.01 T and r ( 20.0 cm, calculate two different electric fields to enable the mass spectrometer to differentiate singly charged copper isotopes and

[3 marks]

[Atomic mass of isotope ( 62.929601 u,

atomic mass of isotope ( 64.927794 u.]

q = 1.6 x 10-19 C / e

( 30.6 V m(1 / 31 V m(1

E2 (

= 29.7 V m(1/ 30 V m(1

(c)(i)Why does a fusion reaction take place at high temperatures?[1 mark]

( need to overcome strong electrostatic repulsion(between nuclei at very small

distance is very high.)

(ii)Calculate the energy released in the following fusion reaction.

+

[Atomic mass of isotope ( 13.003355 u,

atomic mass of isotope ( 1.007825 u,

atomic mass of isotope ( 14.003074 u,

1u ( 931 MeV.]

[3 marks]

E ( (mc2 or (m= mcu + mH - mN

Mass defect (m ( 0.008106 u

The energy released ( 0.008106 ( 931 MeV

( 7.547 MeV/ 1.21 x 10-12 J /7.57 MeV

(d)Explain briefly the controlled fission reaction in a nuclear reactor.[3 marks]

nucleus as a source of fuel

Control rod to absorb excess neutron

Moderator / coolant to decelerate neutron speed

Critical mass / chain reaction

Multiplying factor

S

r

1.2 m

q2 1.0 (C

Ions

(

(

(

y

0

0.3 m

or sum of kinetic energies of particles/atoms/molecules

EMBED Equation.3

B2

B1

EMBED Equation.3

= 2 EMBED Equation.3

EMBED Equation.3

EMBED Equation.3

V1

EMBED Equation.3

R

(

C1

4.4 m s-1

0.3 m

0

t ( 0

EMBED Equation.3

h ( 2 m

x ( 2.8 m

(7.5)

q1

(1.2 (C

P

EMBED Equation.3

EMBED Equation.3

T = 6 hrs

V2

Or

EMBED Equation.3

EMBED Equation.3

EMBED Equation.3

(7.5)

r

Magnetic field to deflect ions

Velocity selector

Ions

5(F

10(F

10 V

C2

40

h

A

60

B (T = 350K)

x

mg (( 5 ( 9.81 ( 49 N)

p

C1

nl ( 1.52

Lens

nc ( 1.38

t

Coating

Gas no order

Liquid no order

Solid orderly for crystalline solid

p1

p2

V

Frep

r

2

Air

na ( 1

1

( + (

(

( + (

T2

T1

Or = EMBED Equation.3

or

any point

Or

R = T cos 30o

R =340 N

Or

EMBED Equation.3

R = 340 N

Or

T sin 30o = 20g

T = 390 N

R

T

O

5.0 kg

60

or

C2

CT = 3.33 (F

x

EMBED Equation.3

EMBED Equation.3

EMBED Equation.3

40

A vector quantity is a quantity having both a magnitude and a direction

20.0 kg

EMBED Equation.3

A

30(

P

1.2 m

0.3 m

0.3 m

q1

(1.2(C

q2

+1.0(C

O

5.0 mm

3.0 mm

3.0 cm

Air

Inside

the house

Outside the house

100o

50o

30o

T2

T1

5g

EMBED Equation.3

mg

(

E

EMBED Equation.3

For 1st quarter, capacitor is charged, energy is stored. (1)

For 2nd quarter, capacitor discharges, energy is returned to the source. (1)

or

For 3rd quarter, capacitor is charged with the opposite polarity, energy is stored. (1)

For 4th quarter, capacitor discharges, energy is returned to the source. (1)

d sin = n

/electron as a wave

EMBED Equation.3

= EMBED Equation.3

EMBED Equation.3 /eV= mv2

EMBED Equation.3

R versus EMBED Equation.3 is a straight line

R

L

EMBED Equation.3

= 300 m s-1

EMBED Equation.3

22

b

23

_1172563073.unknown

_1194256354.unknown

_1194945896.unknown

_1195055004.unknown

_1302715111.unknown

_1302715170.unknown

_1302715373.unknown

_1302714446.unknown

_1195053096.unknown

_1195054133.unknown

_1195054168.unknown

_1195054822.unknown

_1195054863.unknown

_1195054353.unknown

_1195054154.unknown

_1195053149.unknown

_1194978619.unknown

_1194981773.unknown

_1194981795.unknown

_1194981001.unknown

_1194981077.unknown

_1194950378.unknown

_1194978552.unknown

_1194947278.unknown

_1194947332.unknown

_1194946027.unknown

_1194940002.unknown

_1194943609.unknown

_1194943702.unknown

_1194945357.unknown

_1194940081.unknown

_1194943316.unknown

_1194940055.unknown

_1194939870.unknown

_1194939921.unknown

_1194933066.unknown

_1194935314.unknown

_1194931915.unknown

_1194932294.unknown

_1194256858.unknown

_1173011929.unknown

_1174542499.unknown

_1178093504.unknown

_1178095348.unknown

_1178095471.unknown

_1194183351.unknown

_1194241000.unknown

_1178095470.unknown

_1178095340.unknown

_1178007448.unknown

_1178085357.unknown

_1178091315.unknown

_1178091177.unknown

_1178009616.unknown

_1178007455.unknown

_1178007399.unknown

_1178007440.unknown

_1178007420.unknown

_1178007381.unknown

_1174136886.unknown

_1174293564.unknown

_1174293577.unknown

_1174136986.unknown

_1173182011.unknown

_1174132261.unknown

_1174134783.unknown

_1174114409.unknown

_1173011988.unknown

_1172733844.unknown

_1172773489.unknown

_1172816085.unknown

_1172926696.unknown

_1172926759.unknown

_1172991001.unknown

_1172926666.unknown

_1172773566.unknown

_1172773405.unknown

_1172773437.unknown

_1172773337.unknown

_1172773387.unknown

_1172754207.unknown

_1172564235.unknown

_1172566125.unknown

_1172732879.unknown

_1172566099.unknown

_1172566088.unknown

_1172563249.unknown

_1172564222.unknown

_1172563104.unknown

_1171779691.unknown

_1172061417.unknown

_1172131243.unknown

_1172131291.unknown

_1172131326.unknown

_1172131406.unknown

_1172134087.unknown

_1172131381.unknown

_1172131312.unknown

_1172131261.unknown

_1172061647.unknown

_1172125767.unknown

_1172131127.unknown

_1172125748.unknown

_1172061499.unknown

_1171786721.unknown

_1171865007.unknown

_1171865070.unknown

_1171865560.unknown

_1171801421.unknown

_1171864999.unknown

_1171801407.unknown

_1171791061.unknown

_1171781543.unknown

_1171781636.unknown

_1171781673.unknown

_1171781554.unknown

_1171780033.unknown

_1171718152.unknown

_1171778242.unknown

_1171778484.unknown

_1171779035.unknown

_1171779098.unknown

_1171779234.unknown

_1171779074.unknown

_1171778820.unknown

_1171778370.unknown

_1171777676.unknown

_1171777749.unknown

_1171777574.unknown

_1171715434.unknown

_1171716739.unknown

_1171717883.unknown

_1171717983.unknown

_1171717783.unknown

_1171716807.unknown

_1171716613.unknown

_1171716635.unknown

_1171716137.unknown

_1171439575.unknown

_1171714426.unknown

_1171715345.unknown

_1171692481.unknown

_1171712997.unknown

_1171454715.unknown

_1171455246.unknown

_1171350288.unknown

_1171435771.unknown

_1171435889.unknown

_1171435921.unknown

_1171356046.unknown

_1171270171.unknown