Physics Paper 1 Questions and Answers - Form 3 End Term 1 Exams 2022

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INSTRUCTIONS
ANSWER ALL QUESTIONS IN THE SPACE PROVIDED.

  1. 30cm3 of petrol is mixed with 40cm3 of kerosene. If the density of petrol is 0.70gcm3 and kerosene is 0.80gcm3. Calculate the density of the mixture. (3mks)
  2. 60 drops of water are transferred to a beaker from a burette. The level of water in the burette fall from 17cm3 mark to 20cm3 mark. Calculate the volume of I drop of water (3mks)
  3. Name the forces acting on
    1. A box resting on a bench
    2. Between the wheels of a moving car and the road
    3. On an object immersed in water
    4. Between n- pole and s-pole of a magnet
    5. Between water poured on glass and the glass surface.
  4.      
    1. State two practical applications of friction force in our daily lives. (3mks)
    2. List three ways in which friction force can be reduced. (3mks)
  5. The figure below shows a form of a hydraulic lift.
    1
    Using Pascal’s principle, determine the forces F2 on the small piston to lift the load. (4mks)
  6. Study the set-up below and answer the questions that follows
    2
    1. What observation would be made in the tube after some time. (1mk).
    2. Indicate in the diagram the likely position where the observation stated in (a) above would take place. (1mk)
  7.      
    1. When taking care of a lead acid accumulator, what must be done if the
      1. Density of the acid becomes too low. (1mk)
      2. Level of the acid becomes too low. (1mk)
    2. An echo sound sends sound signals to the bottom of a lake and receives them back after 0.08s. Find the depth of the lake. (Take the speed of sound in water 1400m/s) (2mks)
  8. The velocity of light in water is 2.2 x 108ms and the velocity of light in a diamond is 1.24 x.108m/s. Calculate
    1. Retractive index of light passing from water to diamond. (3mks)
    2. The critical angle for water is 48.6º Calculate the refractive index of water. (2mks)
    3. State the applications of total internal reflections.
  9. The figure below shows sound waves emitted by a drum struck.
    Explain why the wave fronts are directed to the around (2mks)
  10. A solid weighs 32.5N on the surface of the moon. The force of gravity on the moon is 1.7Nkg-1. Determine the mass of the solid. (3marks)
  11. The figure below shows a Bunsen – burner.
    3
    Use the Bernoulli’s principle to explain how air is drawn into the burner when the gas tap is opened. (3mks)
  12. Using a well labeled diagrams, show three states of equilibrium. (3mks)
    Define the moment of a force. (2mk)
  13.           
    1. What is a luminar flow? (1mk)
    2. State two assumptions needed in derivation of equation of continuity. (2mks)
    3. State two effects of Bernoulli’s principle. (2mks)
  14.        
    1.        
      1. State Newton’s first law of motion. (1mk)
      2. Give a reason why it is important that passenger’s in moving vehicles put on safety belts. (2mks)
    2.    
      1. A boy of mass 60kg stands on a balance in a lift which is accerating upwards of 2m/s2, Find the balance reading.(3mks)
      2. State kinetic theory of matter. (1mk)
      3. State the condition for total internal reflection to occur. (2mks)
  15. A figure below shows a car decelerating uniformly from a velocity of 10m/s to rest in 2s.
    4
    If it takes 2s to reverse with uniform acceleration to its original starting point, determine the:
    1. displacement of the car 2mkS
    2. average velocity of the car (3marks)
    3. distance travelled by the car (3marks)
    4. average speed of the car (2marks)
  16. An object is placed 30cm from a concave mirror of focal length 20cm. Calculate the magnification. (3mks)
    Explain why it is dangerous for a bus to carry standing passengers. (2mks)
  17.      
    1. A uniform metro rule is balanced at the centre of gravity by a force 30N, 5N and the magnetic force between P, and Q. P is fixed and Q has a weight
      5
      Ignoring the weight of the metre rule, calculate the value of the magnetic force between Q and P. (3mks)
    2. Given that the lower end of Q is North-pole, state the polarity of the end of P facing Q (1mk)
  18.       
    1. Give a reason why water is not suitable as a barometric liquid. (1mk)
    2. Explain why a lift pump is unable to raise water from a borehole where the level of water is 20M below the ground level. (2mks)
    3. State two reasons why gases diffuse faster than solids. (2mks)
  19. The diagram below shows a ray of light travelling between water-glass interfaces.
    Calculate the value of I given that ang=1.52, and anw=4/3 (3mks)


MARKING SCHEME

INSTRUCTIONS
ANSWER ALL QUESTIONS IN THE SPACE PROVIDED.

  1. 30cm3 of petrol is mixed with 40cm3 of kerosene. If the density of petrol is 0.70gcmand kerosene is 0.80gcm3. Calculate the density of the mixture. (3mks)
    Density=   total mass   = pp x vp+pkxvk
                    Total volume          Vp+Vk
    = (0.07x 30+0.08x40)g
    (30+40)cm3
    = (21+32) g
           70cm3
    0.76gcm3
  2. 60 drops of water are transferred to a beaker from a burette. The level of water in the burette fall from 17cm3 mark to 20cm3 mark. Calculate the volume of I drop of water (3mks)
    Volume of 60 drops= (20-17)cm3 = 3cm3
    Volume of a drop = (3/60) cm3
    =0.05cm3
  3. Name the forces acting on
    1. A box resting on a bench
      Reaction force
    2. Between the wheels of a moving car and the road
      Friction force
    3. On an object immersed in water
      Up thrust force
    4. Between n- pole and s-pole of a magnet
      Magnetic force
    5. Between water poured on glass and the glass surface.
      Adhesion force
  4.      
    1. State two practical applications of friction force in our daily lives. (3mks)
      Walking
      braking
    2. List three ways in which friction force can be reduced. (3mks)
      polishing the surface
      lubricating
      use of ball bearing
  5. The figure below shows a form of a hydraulic lift. 
    1
    Using Pascal’s principle, determine the forces F2 on the small piston to lift the load. (4mks)
    F1 = F2 = 100 = F2
    A1    A2    0.25   10
    F2= 100 x 10  = 4,000N
                    0.25
  6. Study the set-up below and answer the questions that follows
    2
    1. What observation would be made in the tube after some time. (1mk).
      A white ring forms in the tube
    2. Indicate in the diagram the likely position where the observation stated in (a) above would take place. (1mk)
  7.      
    1. when taking care of a lead acid accumulator, what must be done if the
      1. Density of the acid becomes too low. (1mk)
        Recharge the battery
      2. Level of the acid becomes too low. (1mk)
        Top up using distilled water
    2. An echo sound sends sound signals to the bottom of a lake and receives them back after 0.08s. Find the depth of the lake. (Take the speed of sound in water 1400m/s) (2mks)
      D= 1⁄2vt=1⁄2 x 1400 x 0.08
      =56m
  8. The velocity of light in water is 2.2 x 108ms and the velocity of light in a diamond is 1.24 x.108m/s. Calculate
    1. Retractive index of light passing from water to diamond. (3mks)
      Wnd =  vol of light in water  
               Vol of light no diamond
      =  2.2x10  8
       1.24 x 108
      =1.774
    2. The critical angle for water is 48.6º. Calculate the refractive index of water. (2mks)
      N=1⁄sin⁡c
      =1⁄48.6º
      1⁄0.7501
      1.53
    3. State the applications of total internal reflections.
      Penscope
      prism binoculars
      Pentaprism
      Optical fibre
  9. Some smoke was enclosed in a smoke cell and observed under a microscope as shown in figure 2. State and explain the observed motion of the smoke particles. (2mks)
    6
    Smoke particles were observed to move in short, random and zigzag paths. ;
    This was due to bombardment by air molecules.
  10. The figure below shows samples of the same liquid B and C being heated through a well – lagged copper rod of non-uniform cross-sectional area. A thermometer is placed in each sample for some time. .
    If the rod is being heated at the middle, state an explain which thermometer record higher temperature. (2mks)
    • Thermometer in the sample B
    • The rate of conductivity of heat increases with cross-sectional area
  11. The figure below shows a Bunsen – burner.
    Use the Bernoulli’s principle to explain how air is drawn into the burner when the gas tap is opened. (3mks)
    • As the gas passes through the nozzle, the velocity increases thus
    • The pressure decrease above the nozzle
    • The higher atmosphere pressure pushes the air into a gas stream
  12. Using a well labeled diagrams, show three states of equilibrium. 3mks
    1. State and explain the type of equilibrium the marble is in (2mks)
      • Ustable
      • Any push causes the marble to roll so as to lower the position of C.O.G
    2. Define the moment of a force. (1mk)
      The product of force and the perpendicular distance from the line of action of force to the turning point. (pivot)
  13.      
    1. What is a luminar flow? (1mk)
      It is the streamline flow with the particles of fluid moving in layers.
    2. State two assumptions needed in derivation of equation of continuity. (2mks)
      The fluid must be incompressible
      The fluid must be non-viscous
      The liquid should have a steady flow
    3. State two effects of Bernoulli’s principle. (2mks)
      Lifting effect
      Blowing roof tops
      Bunsen burner
      Road accidents
      Spray gun
  14.      
    1. State Newton’s first law of motion. (1mk)
      A body in a state of rest remains at rest and if moving continues moving in a straight line unless acted upon by external forces.
    2. Give a reason why it is important that passenger’s in moving vehicles put on safety belts. (2mks)
      in case of emergency breaking of collition, they are held/trapped on their seats.
      this prevents injuries
  15.        
    1. A boy of mass 60kg stands on a balance in a lift which is accerating upwards of 2m/s2, Find the balance reading. (3mks)
      Reaction ( R) = M(ga)
      =60(10x2)
      =720
    2. State kinetic theory of matter. (1mk)
      States that matter is made up of tiny particles which are in random motion
    3. State the condition for total internal reflection to occur. (2mks)
      Incident angle should be greater than article angle
      The light rays should transverse from optically denser medium to less denser medium
  16. A figure below shows a car decelerating uniformly from a velocity of 10m/s to rest in 2s.
    4
    If it takes 2s to reverse with uniform acceleration to its original starting point, determine the:
    1. displacement of the car 2mks
      ½ x 2x (+10) + ½ x 2(-10)
      = (+10 - 10)
      =0
    2. average velocity of the car (3marks)
      average velocity = displacement
                                          time
      =0/4
      =0m/s
    3. distance travelled by the car (3marks)
      area = ½ x 2 x 10 + ½ x 2 x 10
      10 + 10 = 20m
    4. average speed of the car (2marks)
      av. Speed = (distance travelled)
                                time taken
      20/40 = 0.5m/s
  17. An object is placed 30cm from a concave mirror of focal length 20cm. Calculate the magnification. (3mks)
    F=t20 V=+30
    1/f=1/v+1/v, 1/v, 1/v=1/f+1/u
    =1/2-1/30
    1/v= 3-2=
            60   60
    V=+60cm
    M=v/u= 60 
                30
    = 2
    • Explain why it is dangerous for a bus to carry standing passengers. (2mks)
      The centre of gravity (cog) is raised
      This makes the bus unstable (likely topple)
  18.  A uniform metro rule is balanced at the centre of gravity by a force 30N, 5N and the magnetic force between P, and Q. P is fixed and Q has a weight
    7
  19.          
    1. Ignoring the weight of the metre rule, calculate the value of the magnetic force between Q and P. (3mks)
      Σ Acm= Σcm
      3vx20=20xf
      F=600
           30
      =20N
      Magnetic force
      =(20-5)
      =15N
    2. Given that the lower end of Q is North-pole, state the polarity of the end of P facing Q (1mk)
      South pole
  20.        
    1. Give a reason why water is not suitable as a barometric liquid. (1mk)
      It has low density hence need a long column of water to support atmospheric pressure
    2. Explain why a lift pump is unable to raise water from a borehole where the level of water is 20M below the ground level. (2mks)
      The maximum height con be raised is 10M . Reason. The pump operates due to atmospheric pressure
      Reason: The pump operates due to atmospheric pressure
    3. State two reasons why gases diffuse faster than solids. (2mks)
      Gas particles are light and diffuse faster
      Solid particles are held together
  21. The diagram below shows a ray of light travelling between water-glass interfaces.
    8
    Calculate the value of I given that ang=1.52, and anw=4/3 (3mks)
    N1 sin ϴ1=n2 sin ϴ2
    43 sin i=1.52 sin 28º
    Sin I = ¾ x 1.52 sin 28
    I=32.60

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