P2 Sabah 2007 Ans

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  • 8/9/2019 P2 Sabah 2007 Ans

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    ANSWER

    1) (a)(i) 7.7 -3.3 = 4.4 cm

    (ii) - the object to be measured must be touching the meter rule.- avoid parallax error when reading the metre rule.

    (b)

    Physical Quantity MeasurementEarth-Sun distance 1.5 x 108 km

    Thickness of a CD-ROM 0.80 mm

    Height of Mt Kinabalu 4100 m

    Radius of the Earth 6400 km

    Height of an average boy 70 cm

    2) (a)

    (b) weight = mg =(20)(10) = 200 N

    (c) The resultant force acting on a system is zero.(d)

    (e)

    OB

    OB

    OB

    Wsin30

    T

    2000.5

    T

    T 400 N

    =

    =

    =

    3) (a)(i) pressure = 20 /(5 x 10-4)

    = 40 kPa.

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    ANSWER

    (ii) weight of load , W = 20 x (50/5)

    = 200 N.

    (iii) distance moved = (5 x 4)/50= 0.4 cm

    (b)Pascals principle.

    (c) The pistons are frictionless.

    4) (a) C

    (b) (i) The distance of separation between the molecules of gas is greater than in liquid.The force of attractions between molecules is negligible as compared to liquid. Hence

    making gases easier to compress.

    (ii) Latent heat is required to weaken the bond between the molecules in the solid toenable the molecules to move further apart to form liquid.

    (c) the quantity of heat that is required to be absorbed by a substance to change 1 kg of

    the substance in liquid form at its boiling point into its gaseous state.

    (d ) H = m l

    170000 = (0.5) l

    l= 240000 J kg-1

    5) (a) (i) No

    (ii) Rays of light travel from the object to the air is refracted away from the normal.

    The rays of light then enter the eyes of the sailor apparently nearer to the surface of thewater.

    (b)

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    ANSWER

    (c)real depth

    n=apparent depth

    real depth

    1.35=4

    Real depth of object = 5.4 m

    Real depth of the sea = 5.4 + 0.5

    = 5.9 m

    6) (a) Reflection of sound

    (b) (i) Sound with high frequency have high energy and penetrate further into the seawater with little loss of energy.

    (ii)v = f

    1500 = 6.0 x 10 5

    =5100.6

    1500

    x

    = 0.025 m

    (iii)Let d = distance shoal of fish from trawler

    t = 0.2 s , v = 1500 ms 1

    d =2

    vt=

    2

    2.01500x

    = 150 m

    ( c ) To measure the depth of the sea-bed.

    7) (a) I = P/V = 2500/240 = 10.4 A(b) (i) 1.20 mm

    (ii) As resistance is inversely proportional to cross-sectional area, a thinner wire will have

    a higher resistance thus the wire will become very hot. This could probably cause a fire tobreak out.

    (c)Do not operate the kettle with wet hands.

    (d)Short circuit might occur if the insulating materials of the wires in the cable are

    damaged.

    8) (a) The iron core becomes magnetized.

    (b) (i) An electric current is induced in the coil RS(ii) deflects momentarily.

    (c)

    1:8

    30

    240

    =

    =

    =

    Vs

    Vp

    Ns

    Np

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    ANSWER

    d) i) Heat is loss in the coils.ii) Magnetic flux leakage occurs.

    Section B

    9) (a) pressure is the force acting perpendicularly per unit surface area.

    (b) (i) Air bubble displaces water and balloon displaces air. Buoyant force acts on the air

    bubble, buoyant force also acts on the balloon. Both air bubble and balloon rises

    vertically upwards.(ii) When an object displaces fluid, a buoyant force acts on the object.

    (iii) Archimedes Principle.

    (c) A hot air balloon uses a gas bag, with an opening at the bottom called the mouth.Attached to the envelope is a basket carrying the passengers. Mounted above the basket a

    "burner" for heating the air in the gas bag. The hot gas bag displaces the surrounding air

    thus creating an upward buoyant force on it. If the buoyant force is greater than the totalweight of the hot-air balloon, then the hot-air balloon is able to ascend into the air.

    (d)(i) mass of sea water displaced = 1200 x 1000

    = 1.2 x 106 kgvolume = mass/density = (1.2 x 106)/ 1030

    = 1165 m3

    (ii) volume = (1.2 x106) / 1000

    = 1200 m3

    10) (a) The process of converting alternating current into direct current.(b) The diode in Figure 1 is connected in series to the resistor R. The diodes in Figure 2

    are connected in a quadrangle with two junctions connected to the power supply and the

    other two junctions across the resistor R.Both input are alternating current voltages and the outputs are direct currents.Diode in Fig.1 is used as a half-wave rectifier while in Fig.2 the diodes are used as a full-

    wave rectifier.

    (c) Current flows from X P S A B Q R Y(d) Capacitor

    (e)

    Section C

    11) (a) (i) Isotopes are atoms of the same element that have the same number of protonsbut different number of neutrons in the nucleus.

    (ii)

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    ANSWER

    (b) Solubility in water - must be soluble - so that it can dissolve in waterhalf-life - short - so that it doesn't last long to cause any harm to the consumers

    type of radiation - -particles - so that it can be detected by the G=M tube.

    Penetrating power - moderate - so that the radiation can penetrate the ground

    Choice - V because it is soluble in water, have a short half-life, emits -particles and havea moderate penetrating power.

    (c)(i) Average activity = (880+960+940+980+820) / 5 = 916

    (ii) 5hrs 5hrs916 458 229

    Answer : 229

    12) (a) Pascals principle states that the pressure applied to an enclosed fluid istransmitted evenly throughout the fluid.

    (b)When the brake pedal is pressed, pressure exerted in the master cylinder is transmitted

    via the hydraulic fluid to the wheel cylinder thus forcing the brake shoe to function toslow down the car. When the pressure on the foot pedal is released, the spring forces the

    piston back into the wheel cylinder, thereby terminating the contact between the brake

    shoe and the wheel.(c ) (i) rate of wear and tear low so that the brake shoe can last longer. Melting point

    high so that the brake shoe doesnt soften when in use. Coefficient of friction high

    so that the braking is effective. Specific heat capacity low so that the temperature of

    the brake show will not increase dramatically.(ii) Material Q because its rate of wear and tear is low, its melting point is high, its

    coefficient of friction is high and it have a high specific heat capacity.