CBSE Science Class 8 Model Paper From Chapter 11 - Force and Pressure

M.M: 46 marks                                                   Dated: 27/07/2011

Time: 1 hour

Q 1: Fill in the blanks (1 mark per question x 17 = 17 marks)

1. In science, a ______ or a ______ on an object is called a force.
2. Attraction between opposite poles of two magnets is an example of ______.
3. Repulsion between similar poles of two magnets is an example of _________.
4. Forces applied on an object in the same direction ______ to one another.
5. If the two forces act in the ________ directions on an object, the net force acting on it is the difference between the two forces.
6. The strength of a force is called as ____________.
7. The state of ________ is considered to the state of zero speed.
8. The force resulting due to action of muscles is known as _______________ _________.
9. The force of __________ always acts on all the moving objects and its direction is always ________ to the direction of motion.
10. ______ poles of magnet repel each other and _______ poles of magnet attract each other.
11. Muscular force is also known as __________ force as it can be applied only when it is in contact with an object.
12. The force exerted by a magnet is an example of ____________ force.
13. The force exerted by a charged body on other charges or uncharged body is known as _____________ force.
14. Objects thrown upward falls toward earth because of force of ___________.
15. Pressure exerted by water at the bottom of the container depends on the __________ of its column.
16. Liquids exert __________ pressure at the same depth of a container.
17. The envelop of air all around us is known as ______________.

Q 2: Tick True or False, also correct the false statements wherever needed by writing the correct answer.  (1 mark per question x 4 = 4 marks)

1. Gases exert no pressure at the walls of their container – True/False
2. The pressure exerted by air around us is known as troposphere pressure – True/False
3. Force only has magnitude and no direction - True/False
4. There is only one force acting on a just launched satellite from Earth – True/False

Q 3: Give an example of a task where either push or pull can complete the task.                                                                   (1 mark)

Q 4: How many objects at least should be there for force to come into play?                                                                                 (1 mark)

Q 5: What will be the net force acting on an object on which two equal and opposite forces are acting?                                     (1 mark)

Q 6: When do forces get added?                                            (1 mark)

Q 7: When will the speed of an object on which force is applied increases?                                                                                (1 mark)

Q 8: What is the change in state of motion?                           (1 mark)

Q 9: What could be the results of applying force on an object?                  (2 marks)

Q 10: What brings a boat to stop after sometime after rowing is not done?                                                                                       (1 mark)

Q 11: Is it always necessary for the agent applying a force on an object to be always in contact with it? Explain with an example.                                                                                                        (2 marks)

 Q 12: What happens when a straw rubbed with paper is brought near an unrubbed hanging straw of similar type? What happens when the free end of hanging straw is now rubbed with paper and then the free end of straw rubbed with paper is brought near it?               (2 marks)

Q 13: Define pressure. What is its SI unit?                           (2 marks)

Q 14: Why do porters put a round piece of cloth on their heads when they have to carry load?                                                        (2 marks)

Q 15: How will you prove that water exerts pressure on the sides of the container?                                                                        (2 marks)

Q 16: Explain the working of an ink dropper in brief.         (2 marks)

Q 17: Identify the agent exerting the force and the object on which it acts in the following scenario. Also state the effect of force.                                                                                                              (2 marks)

1. Squeezing of lemon by a person fingers

Q 18: Calculate force acting on an object when the pressure on it is 11 pascal and its area is 100cm2.                                         (2 marks)

Synthetic Fibres & Plastics Model Science Paper of CBSE, NCERT Class 8th

Science Class 8th Test From Chapter 3 – Synthetic Fibres and Plastics

M.M: 41 marks                                                   Dated: 02/07/2011

Time: 1 hour

Q 1: Fill in the blanks (1 mark each x 17 = 17 marks, depending on your answer, more than one word may come at certain blanks).

 i.   A very thin, thread like strand from which cloth is produced 

in called a ______________.

ii. Based on the source from which the fibres are obtained, there can be two types of fabrics: ____________ and ____________.

iii. The three R’s, i.e. RRR, used to save the environment from the harmful effects of excessive use of plastics, stand for ____________, _____________ and ______________.

iv. The use of plastics can be minimised by using bags of _______________ or ____________ instead of polythene bags.

v. The full form of PVC is _______ _________ _____________.

vi. In ______________, the long polymer chains are not cross linked with each other.

vii.  ______________ plastics are used for making articles which cannot get hot during use and are hard and rigid too.

viii.  ___________ is a type of plastic on which oil and water does not stick and can withstand high temperatures.

ix. __________ is a type of plastic which is very hard, tough, poor conductor of heat and electricity and is used for making the handles of various cooking utensils.

x. Synthetic fibres are produced from raw materials called ________________.

xi. Synthetic fibres are also called ___________ or ___________ fibres.

xii. ______________ is a synthetic fibre produced from chemical “acrylonitrile’, is soft, warm with a feel like wool.

xiii. PET stands for ______________ __________________.

xiv. _____________ is made of repeating units of chemical called ester.

xv.  The name NYLON is based on the fact that it was developed in _______________ and __________.

xvi.  _____________ is often regarded as artificial silk.

xvii. A ___________ is a very big molecule which is formed by combining large number of small molecules.

Q 2: Give two examples each of synthetic and natural fibres. 

(2 marks)

Q 3: Define petrochemicals. Give two examples.                (2 marks)

Q 4: Is Rayon an artificial fibre or a natural fibre? How is it different from truly synthetic fibres?                                   (2 marks)

Q 5: Which was the first fully synthetic fibre made by man without any use of natural raw material? Write two uses of the same.

(2 marks)

Q 6: What is polycot and polywool made of?                       (1 mark)

Q 7: Write two properties of PET and two uses of the same.

(2 marks)

Q 8: Write two pros and two cons of synthetic fibres.        (2 marks)

Q 9: Write one difference between thermosetting plastics and thermoplastics. Write two examples of both of them.        (3 marks)

Q 10: Show arrangement of polymer chains in thermoplastics and thermosetting plastics.                                                         (2 marks)

Q 11: Which of the following articles made of plastics “Cannot be recycled” and which “Can be recycled”? Items: Telephone instruments, Plastic chairs, Carry bags, Electrical switches, Ball point pens, Plastic insulation on electrical wires.                 (3 marks)

Q 12: What do you understand by non-biodegradable and biodegradable materials? Give two examples of each.       (3 marks)

Crop Production & Management Model Paper Of CBSE Science Class 8th

M.M: 48 marks                                                                                Dated: 01/07/2011




                 

                                                                 

Time: 1 ½ hour

Q 1: Fill in the blanks                                          (1 mark per question x 18 = 18 marks)

1. The activities or tasks undertaken by farmers for cultivation of crops are known as __________ ______________.
2. Separation of grains from the chaff is called _____________.
3. ____________ involves removal of unwanted and uncultivated plants called _________.
4. We get _______ ______ oil from fish which is rich in vitamin_______.
5. Large scale storage of grains is done in __________ and ____________ to protect them from pests.
6. Farmers with small holdings of land do the separation of grain and chaff by _____________.
7. Special festivals associated with the harvest season are ____________ and ____________.
8. One example of a weedicide is _______________.
9. Weedicides are sprayed during the vegetative growth of weeds before ______________ and _______ formation.
10. Two traditional methods of irrigation are _____________ and __________.
11. Plants contain nearly ________ water.
12. __________ ____________ are present in the nodules of the roots of leguminous plants.
13. Two examples of fertilisers are ___________ and _____________.
14. With reference to fertilisers, NPK stands for ___________, ___________ and ____________.
15. ______________ is the most important part of crop production.
16. Nowadays, ploughing is done by tractor driven _______________.
17. The process of loosening and turning of the soil is called __________ or ___________.
18. The levelling of soil is done with the help of a ____________.

Q 2: Define crop. What are the two broad cropping patterns in India? Give two examples of each.                                                                                                                (3 marks)

Q 3: How many activities are necessary for cultivation of crops? Write their names. 
(4 marks)

Q 4: Why soil is turned and loosened?                                                                 (2 marks)

Q 5: Define animal husbandry.                                                                            (1 mark)

Q 6: Write the names of two places where large scale storage of grains is done. What is the main difference between them?                                                                          (2 marks)

Q 7: What are weeds? How are crops protected from weeds? Write two ways to do so.       (3 marks)

Q 8: What do you understand by harvesting? How is it done? Name two tools used for harvesting in India?                                                                                          (3 marks)

Q 9: What is a combine?                                                                                   (1 mark)

Q 10: Why is it important to properly dry the fresh grains before storing them? What is used by farmers to store food grains at home?                                                            (2 marks)

Q 11: Write names of two modern methods of irrigation. Write one major difference between them.                                                                                                  (3 marks)

Q 12: Write two differences between fertiliser and manure.                                  (2 marks)

Q 13: What is crop rotation and why is it done?                                                   (2 marks)

Q 14: What will happen if mustard is grown in rainy season? Explain.                    (2 marks)