Tuesday, July 26, 2011

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)