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SECTION A (25 marks)

Answer ALL the questions in this section in the spaces provided.

  1. Figure 1, shows a ray of light incident on a plane mirror at O. The mirror is then rotated anticlockwise about O from position M to position M2 through an angle of 10°. The final reflected rayisOC.


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Determine the angle of deviation BOC.

  1. Figure 2(a), shows a magnetic compass placed under a horizontal wire XY

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A large current is passed from X to Y. Draw the final position of the magnetic compass needle in figure

3. Figure 3, shows a diagram of a current-carrying wire wound on a U-shaped soft iron


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Draw the magnetic field pattern around P and Q.

 

4.  A positively charged sphere is suspended by an insulating thread. A negatively charged

conductor is suspended near it. The conductor is first attracted, after touching the

sphere it is repelled. Explain this observation.  

5.  Figure 4, shows a bright electric lamp placed behind a screen which has a hole covered with a wire gauze. A concave mirror of focal length 25cm is placed in front of the screen. The position of the mirror is adjusted until a sharp image of the gauze is formed on the screen.


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Determine the distance between the mirror and the screen.

6 Explain why electric power is transmitted over long distances at high voltages.

7.  Figure 5, shows how the displacement of a point varies with time as a wave passes it.


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On the same diagram, draw a wave which passes the point with half the amplitude and twice
the frequency of the one shown.  

8.  A water wave of wavelength 18 mm is incident on a boundary of shallow water at right
angles. If the wavelength in the shallow end is 14.4 mm, determine the refractive index of
water for a wave moving from the deep to the shallow end.  

9.  The initial mass of a radioactive substance is 20g. The substance has a half-life of 5 years.
Determine the mass remaining after 20 years.  

10. A current I flowing through a wire of resistance R was increased seven times. Determine the
factor by which the rate of heat production was increased.  

11 Figure 6, shows a horizontal conductor in a magnetic field parallel to the plane of the paper.

Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.com

 

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State the direction in which the wire may be moved so that the induced current is in the
direction shown by the arrow.  

12. An x-ray tube produces soft x-rays. State the adjustment that may be made so that the tube
produces hard x-rays.  

13. The wavelength of a radio wave is 1km. Determine its frequency. (Take the speed of light as 3.0 x 108 ms”1)

14. Figure 7, shows a block diagram of a p-n junction diode.

 

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On the same diagram, show how a battery may be connected so that the diode is reverse biased.

 

 

SECTION B (55 marks)

Answer ALL the questions in this section in the spaces provided. 15

15. (a) Figure 8, shows a ckcuit that may be used to charge a capacitor.

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  (i) state the observation on the milliameter when the circuit is switched on:

(ii) explain the observation in (i) above.  

(b) The circuit in figure 8 is left on for some time. State the value of p.d. across:

(i) the resistor R;  

(ii) the capacitor C;  

(c) sketch the graph of potential difference (V) across R against time.  

(d) Figure 9 shows three capacitors connected to a 10V battery.


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Calculate:

(i) the combined capacitance of the three capacitors;

(ii) the charge on the 5.0 juF capacitor.

(b) Figure 11, shows a pin 60 mm long placed along the principal axis of the lens used in part (a). The near end of the pin is 80 mm from the lens


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Determine the length of the image.

 

17 (a) Figure 12, shows an electrical circuit including three switches, Sj, S2, S3, and three identical lamps L,, L2, L3. A constant potential difference is applied across X and Y.


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 (i) Other than Lj, state the lamp that will light when S: and S2 are closed.

(ii) How does the brightness of Ll
in (i) above compare with its brightness when all the switches are closed?  

(iii) Explain the observation in part (ii) above.

 

 

Image From EcoleBooks.com (b) Figure 13, shows a cell in series with a 3Q resistor and a switch. A hig resistance voltmeter is connected across the cell.

Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.com

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Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.com 3Ω

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Image From EcoleBooks.comFigure 13

The voltmeter reads 1.5V with the switch open and 1.2V with the switch closed.

(i) State the electromotive force of the cell.  

(ii) Determine the current through the 3Q resistor when the switch is closed.

(iii) Determine the internal resistance of the cell.

(c)(i) Another resistor R is connected in series with the 3Q resistor so that a current of 0.15A flows when the switch is closed. Determine the resistance of R.

18. Figure 14a, is a diagram of a cathode ray tube. M and N are parallel vertical plates.


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(a) When switch S is open, a spot is seen at the centre of the screen as shown in figure 14(b).
(i) State what happens to the spot when S is closed.  

(ii) State what would happen to the spot if the potential difference across MN is
increased.

(iii) State what would be seen on the screen if the battery is replaced with an alternating emf of:

(I) a low frequency of about 1 Hz;  

(II) a high frequency of about 50Hz.

(b) Explain the process by which electrons are produced at F.  

(c) State with a reason how the brightness of the spot can be increased.  

(d) The accelerating voltage of the tube is 1000V and the electron current in the beam is 1.5mA. Determine the energy conveyed to the screen per second.)

19.
(a) State the property of radiation that determines the number of electrons emitted
when a radiation falls on a metal surface.

 

(b) Figure 15 is a graph of the stopping potential Vs against frequency in an experiment on photoelectric effect.

 

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(i) What is meant by stopping potential?  

(ii) Given that the stopping potential Vs is related to the frequency by the equation.

V s = h f – w
0 Where e is the charge of an electron, (e = 1 .6 x 10′19C)

  e e

Determine from the graph:

(I) plank’s constant, h;  

(II) the work function co0 for the metal in electron volts (eV).

 

 

PHYSICS P 1 2011

QUESTIONS AND MARKING SCHEMES

SECTION A (25 marks)

Answer all the questions in this section in the spaces provided.

1. Figure 1 shows a lorry moving on an inclined section of a straight road. At the back is a chain hanging from a point on a horizontal axis through the centre of gravity of the lorry.

 

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Lorry

Chain

Inclined .road

 

Figure 1

 

(1 mark)

State with a reason whether the lorry is stable or not stable.

 

Stable –center of gravity is within base of lorry . or

Line of action of weight is within the base

2. State the constant force that opposes the motion of a stone initially at rest, as it falls through
air from a tall building .  ( 1 mark)

 


upthrust

 

3. Figure 2 shows a spring balance. It’s spring constant is 125Nm-1. The scale spreads over a distance of 20cm.

 

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Determine the maximum weight that can be measured using this spring.  (3 marks

 

 

F= Ke OR F=Ke

=125 X0.2 125 x 20

= 25 N 100

  =25N

4. Figure 3 shows an aluminum tube tightly stuck in a steel tube .

 

 


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5 Explain how the two tubes can be separated by applying a temperature change at the junction given that aluminium expands more than steel for the same temperature rise.

 


Cooling / reduced temp

(2 marks)

Aluminium contracts more /faster than steel

 

 

Figure 4 shows two identical beakers P and Q full of water at 90°C. Two similar cold wet clothes are wrapped, one around the top of P and the other around the bottom of Q.

 

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Cold wet-cloth

Cold wet cloth

Water-

 

Figure 4

 

 

State with a reason, the,beaker in which the water cools faster. (2 marks)

 

 

P – cool layers from top descend and are replaced

By hot layers OR

There is complete convection currents in p

6. Figure 5 is a graph of net force on a body against it’s, velocity as it falls through a liquid.

 


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Figure 5

 

 

Determine the terminal velocity of the body. (1 mark)

 

80m/s

 

 

7. Figure 6 shows a small toy boat floating on water in a basin. X and Y are-two points near

the toy.

 

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X

 

Water

 

Figure 6

 

When a hot metal rod is dipped into the water at point X, the toy is observed to move
towards Y. Explain this observation.  (2 marks)

Surface tension at x is reduced / weakened / broken

 

Higher surface tension at y pulls the boat.

 

8. When the temperature of a gas in a closed container is raised, the pressure of the gas increases. Explain how the molecules of the gas cause the increase in pressure.

(2 marks)

 

-speed of molecules increases / k.e increases / molecules move faster

 

-Molecules hit walls more frequently /with greater momentum /more collision per unit time

 

9. Figure 7 shows part of a petrol engine, in which air flowing under atmospheric pressure passes into a constriction, where it mixes with petrol. The mixture then flows into a

combustion cylinder.

Atmospheric pressure

 

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Atmospheric pressure

Constriction

Combustion cylinder

Petrol/air mixture

Petrol

Petrol chamber

I—«Piston moving down

 

Figure 7

 

Explain what causes the petrol to move from the petrol chamber to the air stream in the
constriction when the piston is moved downwards. (2 marks


Air speed /verocity is higher at contraction

Pressure drops, higher pa pushes the petro either

Pressure drops or (atmospheric pressure ) pushes the petro

 

10. State the reason why it is easier to separate water into drops than to separate a solid

into smaller pieces. (1 mark

 

smaller /weaker intermolecular forces in liquids than solids or

 

smaller cohesive in liquids than in solids

 

Figure 8 shows a unifonn wooden block of mass 2kg and length 25cm lying on a bench. It hangs over the edge of the bench by 10cm. Use the figure to answer questions 11 and 12.

 

 

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11. Indicate on the figure two forces acting on the wooden block.

 

12. Determine the minimum force that can be applied on the wooden block to make it turn

about the edge of the bench.   (2 marks)

sum of clockwise moments = sum of antclockwise moments

OR F1d1 =
F2d2

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20 x2.5 = F x 10 or F x15 = 20 x 2.5

F= 5N F =3.33N (must be I three sig. fig

13. A particle starts from rest and accelerates uniformly in a straight line. After 3 seconds it

is 9m from the starting point. Determine the acceleration of the particle. (3 marks)

 

S=ut + ½ at3 OR v =u+ at OR v = u+at OR S = 1/2 (u+v)t

9 =0 + ½ x a 32 s = ½(u +v)t v = 3a 9= ½ x 3v

V= 6m/s v2= u2 + 2as v =6 m/s

A = 2m/s2 a = v – u 9a2= 0+2a9 v =u +at

t a2 =2a 6= 0 +a x 3


= 6- 0 a = 0 or 2 a = 2 m/s2

3 a = 2m/s2

= 2 m/s2

14. Figure 9 shows a syringe full of water. It has two identical holes A and B drilled along it’s cylinder. The cylinder nozzle is closed.


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State with a reason how the speeds of the jets of water from A and B compare when
the piston is pushed into the cylinder.

 

Identical jets / same speed

 

Pressure at sama level is equal / pressure is transmitted equally throughout the liquid

 

 

 

 

SECTION B: (55 marks)

 

Answer all questions in this section

 

 

15. Figure 10 shows a simple pendulum of length 80cm. The pendulum bob whose mass is 50g oscillates between points A and B, through its rest position C. A and are both 10cm higher than C.

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Figure 10

Arrow ,horizontal line and straight line

(a) (i)  Indicate with an arrow, on the path ACB, the direction of the greatest

 velocity of the bob as it moves from A to B. (1 mark

 

 

(ii)  State the form of energy possessed by the pendulum bob at point A.

1mark)


Potential energy / potential/ P. E

 

(b)Determine: 3marks

 

  1. the velocity of the bob at point C

 

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  1. the tension in the string as the bob passes point C

(take acceleration due to gravity g – 10 m/s2)

 


T = mv2
+ mg

R

= 0.005 x 2 + 0.005 x 10

8

= 0.0625N

 

 

c) After some time, the pendulum comes to rest at point C. State what happens to the energy it initially possessed.   (1 mark)

 

used to do work against / air resistance /viscous drag / air friction

or converted to heat energy

 

 

16. Figure 11 shows a stone attached to the end of a string moving in a horizontal circle with a uniform speed of 2ms-1. When the stone reaches point X on the circle, the string breaks.

 

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Figure 11

NB: tangent can be drawn facing the other side /must be straight (ruler used) and if extended should not cut the circle

 

(i) Indicate on the diagram with an arrow, the direction of the motion of the stone
when the string breaks. (1 mark)

  1. mark)

 

(ii) State the magnitude of the velocity after the string breaks.

2m/s

(iii)Give a reason for your answers in (i) and (ii) (1mark

 


Obeys Newtons first law of motion / due to its inertial /no external force act

on it /centripetal force is zero (does not act on it

 

(b) Figure 12 shows a lorry towing a trailer using a rope.

 

 


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The lorry exerts a force N on the trailer and the trailer exerts an equal but opposite force M on the lorry. The frictional force between the trailer and the road is F.

 

Explain how the forces N, M and F enable the trailer to move. (2 marks

 


N > F

 

M does not act on the trailer

 

 

 

(c) Figure 13 shows a frictionless trolley of mass 2kg moving with uniform velocity towards a wall. At the front of the trolley is a spring whose spring constant is 25Nm-1. The trolley comes to rest momentarily after compressing the spring by 3cm and then rebounds from the wall.

 

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Figure 13

  1. Determine

 

(I) the force exerted on the wall by the spring. (3 marks)

 


F = ke

= 25 x 30 = 0.75 N

100

 

(II) the maximum acceleration of the trolley as it rebounds from the wall.

(3 marks)

F = ma

0.75 = 2a

A = 0.375m/s2

 

  1. State the reason why the trolley acquires a constant velocity after it rebounds. (2 marks)

Force is the spring decreases as it recovers its original length

No force on the trolley after contact with wall b lost

 

 

17. (a) When the temperature of water reaches the boiling point, bubbles rise to the surface.

 

(i) State what is contained in the bubbles.   (1 mark)

 


Water vapour / steam

 

(ii) State the reason why bubbles rise to the surface only at the boiling point. (1 mark)


Vapour pressure at boiling point exceeds prevailing / external pressure

 

 

b) Figure 14 shows a graph of vapour pressure against the temperature of water vapour, in a laboratory where a mercury barometer indicates a height of 61.8 cm.

Figure 14

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(b) (i) Determine the atmospheric pressure in the laboratory in Nm -2

(Take g – 10m/S2and density of mercury – 13600 kg/m3). (3 marks)

 


P = pgh

= 13600 x 10 x 61.8

100

=840 x 103 N/m3 or 84040N/m2

 

(ii) Use the graph to determine the boiling point of water in the laboratory. (1mark)

 

 


Reading of BP at p = 84 x 103 is 96 + 10c

 

 

 

 

(c) In an experiment to determine the specific heat capacity of a metal, a100g of the

metal was transferred from boiling water to a lagged copper calorimeter containing cold water. The water was stirred and a final steady temperature was realized. The following data was recorded.

Initial temperature of cold water and calorimeter = 20°C.

Temperature of boiling water = 99°C.

Final temperature of water, calorimeter and the metal = 27.7°C.

Mass of cold water and calorimeter = 130g.

Mass of calorimeter = 50g.

(Take specific heat capacity of water as 4200Jkg-1K-1) (Specific heat capacity of copper as 400Jkg-1K-1).

 

Use the data to determine:

(i) the heat gained by the water and the calorimeter;  (3 marks)



MwCwD0 + Mcccdo =

0.08 x 4200 x( 27.7 -20 ) + 0.05 x 400 x (27.7 – 20)

= 2741.2 j

 

(ii) the specific heat capacity of the metal.  (3 marks)

 


Heat lost by metal = heat gained by water + calorimeter

0.1x 71.3 x c = 2741.2


c = 2741.2 =384.46J/kgk

7.13 (384J/kgk)

 

(d) State one possible source of error in the value of the specific heat capacity

obtained in the experiment.   (1 mark)

 


metal cooling is the process of transferring or

metal carrying some hot water into the cold water

18. (a) Figure 15 shows a metal bolt which is threaded.

 

 


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Explain how a metre rule can be used to measure The pitch (distance between  
adjacent peaks) of the threading. (2 marks)

 

  • Measure the length of threaded part
  • Divide the length by number of threads /pitches divide by number of peaks – 1

     

    (b) Figure 16 shows a screw jack whose screw has a pitch of .limn, and has a handle of 25 cm long.

     


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    Determine the velocity ratio of the jack. (3marks)

     

    VR = 2 Πr

    Pitch

    = 2 x 3.142 x0.25 = 1571.43

    0.001

     

    (c) A bullet of mass 60g travelling at 800ms-1 hits a tree and penetrates a depth of

    15 cm before coming.to rest

     

    (i) Explain how the energy of the bullet changes as it penetrates the tree. (1 mark)

    Image From EcoleBooks.comImage From EcoleBooks.com
    K.E =heat + sound OR K.E heat , sound OR K.E heat ,sound( light)

    (ii) determine the average retarding force on the bullet.

     

     

    K.E = work done against friction OR f = ma

    ½ mv2 = fd v2 =u2 +2as

    ½ x0.006 x 8002 =f x 0.15 o = 8002 + 2 x0.15a

    F= 12800N a =640000 =2.133333.3(2.13 x106)

    0.3

    F = ma = 2.133x 1064 x 60

    1000

     

     

    19. (a) State the condition necessary for a body to float in a fluid . (1 mark)

    Upthrust = weight or

    Weight of fluid displaced = weight of the body or

    Its density is less than that of the fluid .

    (b) A ship made of steel is observed to float on water yet the density of steel

    is approximately eight times that of water. Explain this observation. (2 marks)

     

    ship has a large air space / hollow or

    Average density of the ship is less than density of water

    Upthrust of ship is equal to weight of the ship

     

     

    (c) Figure 17 shows three stages of an experiment to determine relative density of

    cork which normally floats on water. To make it sink, a sinker is hung below the cork.

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Spring balance

Figure 17

 

In (I) a spring balance is used to measure the weight W of the cork in air.

In (II) the spring balance is used to measure the apparent weight W1, when only the

sinker is submerged in water.

In (III) the spring balance is used to measure the apparent weight W2 when both the

cork and the sinker are submerged.

The following observations were made.

W = 0.08 N

W1 = 0.060 N

W2 = 0.28 N

Use this information to determine the:

 

(i) upthrust on cork. (3marks)

 


Upthrust = w1 – w2

= 0.60-0.28

= 0.32 N

 

(ii) relative density of cork. (3 marks

 

RD = weight of substance = wt of cork

Weight of equal volume upthrust

 

= 0.08

0.32

= 0.25

 

 

(d) Figure 18 shows parts of a simple submarine, a ship that can travel both on water

and under water.

To do this water is pumped in or out of the ballast tanks.

 

 

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Explain how the tanks are used to change the depth of the submarine. 2 marks)

 

 


To sink , water is allowed into ballast tanks

 

To float , pumps are used to expel water from ballast tanks

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 




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EcoleBooks | K.C.S.E YEAR 2010 PHYSICS PAPER 2

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