Physics Questions and Answers - Form 1 End Term 1 2021

PHYSICS
FORM 1
END TERM EXAM
TERM 1 2021

INSTRUCTIONS

• Answer all the questions

1. Distinguish between basic and derived quantity. Give two examples in each case. (4mks)
2. Complete the table below. (7mks)
   

   QUANTITY	SI UNITS	SYMBOL OF SI UNITS
   LUMINOUS INTENSITY
   	AMPERE
   		K
   	KILOGRAM
   		S
   	MOLE
   LENGTH

3. Explain instances where physics is related with the following. (4mks)
   1. Biology-
   2. Geography-
4. A test-tube has a diameter of 3cm. how many turns would a piece of thread of length 90.42cm make round the test tube.(Take π=22/7) . (3mks)
5. Define the following branches of physics. (4mks)
   1. Waves-
   2. Mechanics-
6.    
   1. Draw a burette filled with water to a volume of 28cm3. (2mks)
   2. 60 drops fell from a burette. The first and final readings were 28cm3 and 42cm3 respectively. What is the average volume of one drop. (3mks)
7. Differentiate between vector and scalar quantity giving relevant examples in each case. (4mks)
8. Determine the density in SI Units of a solid of mass 40g with dimensions 30cm by 4cm by 3cm. (4mks)
9. Define surface tension and state two factors affecting surface tension. (3mks)
10. State two major differences between mass and weight. (4mks)
11. 1600cm³ of fresh water of density 1g/cm³ are mixed with 1200cm³ of sea water of density 1.2g/cm³. Determine the density of the mixture. (4mks)
12. A body weighs 65N. Calculate it’s mass.(g=10N/Kg) (2mks)
13.    
    1. Define pressure giving its SI Units. (2mks)
    2. State any two factors affecting pressure in liquids. (2mks)
14. A block measuring 20cm by 10cm by 5cm rests on a flat surface. The block has a weight of 3N. Determine the maximum pressure it exerts on the surface. (3mks)
15.    
    1. Define force and state its SI Units. (2mks)
    2. Find the resultant of a force 4N and 8N acting at the same point on an object if the forces act in the same direction in the same straight line. (2mks)
16. Explain the following observations:
    1. Water wets glass surface but does not wet the waxed glass surface. (2mks)
    2. A steel needle placed carefully on the surface of water does not sink. (2mks)
    3. A matchstick rubbed at one end with soap starts moving immediately in one direction when placed on the surface of water. (2mks)
    4. The mass of a lump of gold is constant everywhere, but its weight is not. (1mk)
    5. Large mercury drops form oval balls on a glass slide. (2mks)
17. A sphere of diameter 6.0cm is moulded into a thin uniform wire of diameter 0.2mm. Calculate the length of the wire in metres. ( Take π=22/7) (3mks)
18. An astronaut weighs 900N on earth. On the moon, he weighs 150N.caculate the moons’ gravitational strength. (3mks)

MARKING SCHEME

1. Distinguish between basic and derived quantity. Give two examples in each case. (4mks)
   • basic quantity- quantity that cannot be obtained from any other physical quantity. Eg mass, lenth, time, etc.any two..
   • Derived quantity.—quatities that can be obtained from other physical quantities by multiplication or division. Eg weight,force,speed, density etc any correct two.
2. Complete the table below. (7mks)
   

   QUANTITY	SI UNITS	SYMBOL OF SI UNITS
   LUMINOUS INTENSITY	Candela	cd
   Current electricity	AMPERE	A
   Temperature	Kelvin	K
   Mass	KILOGRAM	kg
   Time	Seconds	S
   Amount of substance	MOLE	mol
   LENGTH	metre	m

3. Explain instances where physics is related with the following. (4mks)
   1. Biology- knowledge of lenses in physics is used in the construction of microscope which is used in the study of the cell.
   2. Geography- heat transfer by convection explains the information of convectional rainfall and pressure carnations.
4. A test-tube has a diameter of 3cm. how many turns would a piece of thread of length 90.42cm make round the test tube.(Take π=22/7) . (3mks)
   • C=Πd    22/7x3 cm=9.43cm. NO of turns= 90.42cm/9.43cm= 9.58 turns.
5. Define the following branches of physics. (4mks)
   1. Waves- study of propagation of energy through space.
   2. Mechanics- involves the study of motion of bodies under the influence of forces.
6.    
   1. Draw a burette filled with water to a volume of 28cm³. (2mks)
   2. 60 drops fell from a burette. The first and final readings were 28cm3 and 42cm³ respectively. What is the average volume of one drop. (3mks)
      • 42-21= 21
        21/60=7/20
        = 0.35cm³
        
        
7. Differentiate between vector and scalar quantity giving relevant examples in each case. (4mks)
   • Scalar quantity- has only magnitude and no direction. Eg mass,length, volume..etc
   • Vector quantity- has both magnitude and direction. velocity, force, weight, displacement.
8. Determine the density in SI Units of a solid of mass 40g with dimensions 30cm by 4cm by 3cm. (4mks)
   • Density=mass/volume.
   • Mass=40g, volume= 30cm x4cm x 3cm=360cm³
   • 40g/360cm³=0.11g/cm³ x 1000kg/m3=110kg/m³
9. Define surface tension and state two factors affecting surface tension. (3mks)
   • Behavior of the surface of the liquid to act as a stretched elastic skin. Temperature, impurities.
10. State two major differences between mass and weight. (4mks)
    • Mass- constant everywhere, SI UNITS Kg, scalar quantity.
    • Weight; varies from planet to planet, si units N, Vector quantity.
11. 1600cm³ of fresh water of density 1g/cm³ are mixed with 1200cm³ of sea water of density 1.2g/cm³. Determine the density of the mixture. (4mks)
    • mass of fresh water =1600g, mass of sea water=1440g, total mass=3040g
    • Total vol of mixture=2800cm³
    • Density=mass/volume; 3040g/2800cm3=1.0857g/cm³=1085.7kg/m³
12. A body weighs 65N. Calculate it’s mass.(g=10N/Kg) (2mks)
    • F=Mg; m=F/g  M=65/10 = 6.5Kg.
      
      
13.    
    1. Define pressure giving its SI Units. (2mks)
       • p=F/A SI UNITS N/M².
         
    2. State any two factors affecting pressure in liquids. (2mks)
       • Depth, area etc
         
14. A block measuring 20cm by 10cm by 5cm rests on a flat surface. The block has a weight of 3N. Determine the maximum pressure it exerts on the surface. (3mks)
    • A=0.1X0.05=0.005M², F=3N, P=F/A   P= 3/0.005= 600N/M².
15.    
    1. Define force and state its SI Units. (2mks)
       • push or a pull. SI Units Newtons (N).  
    2. Find the resultant of a force 4N and 8N acting at the same point on an object if the forces act in the same direction in the same straight line. (2mks)
       • 4N+8N=12N
         
         
16. Explain the following observations:
    1. Water wets glass surface but does not wet the waxed glass surface. (2mks)
       • water wets glass-adhesive force is stronger between water molecules and glass molecules.
    2. A steel needle placed carefully on the surface of water does not sink. (2mks)
       • surface of water acts/appears like an elastic stretched 2km due to forces of surface    tension.
    3. A matchstick rubbed at one end with soap starts moving immediately in one direction when placed on the surface of water. (2mks)
       • soap at the end of the stick immediately dissolves in water hence lowering surface tension      at the end of the stick. Surface tension at the other end pulls the stick and makes it move in that direction.
    4. The mass of a lump of gold is constant everywhere, but its weight is not. (1mk)
       • Mass is constant everywhere because the number of particles in an object does not change. Weight is different due to change in the force due to gravity from earth a moon.
    5. Large mercury drops form oval balls on a glass slide. (2mks)
       • cohesive force between mercury molecules is stronger than the adhesive forces,.
17. A sphere of diameter 6.0cm is moulded into a thin uniform wire of diameter 0.2mm. Calculate the length of the wire in metres. ( Take π=22/7) (3mks)
    • volume of sphere=4/3πr3 =4/3x22/7 x3x3x3.
    • Volume of wire=πr2l=22/7x0.01x0.01 xl
    • Volume of sphere =volume of wire.
    • L=3x3x3x3/3x0.01x0.01 =3600m
18. An astronaut weighs 900N on earth. On the moon, he weighs 150N.caculate the moons’ gravitational strength. (3mks)
    • mass of astronaut=w/g= 900N/10N/Kg =90Kg.
    • Weight on moon.= 150N, mass=90Kg, g=150N/90Kg =1.67N/Kg.