Monday, September 6, 2021

NCERT Exemplar Class 8 Chapter 11 – Force And Pressure

Multiple Choice Questions

1. In Fig 11.1, two boys A and B are shown applying force on a block. If the block moves towards the right, which one of the following statements is correct?

(a) The magnitude of force applied by A is greater than that of B.

(b) The magnitude of force applied by A is smaller than that of B.

(c) The net force on the block is towards A.

(d) The magnitude of force applied by A is equal to that of B.



2. In the circuit shown in Fig.11.2, when the circuit is completed, the hammer strikes the gong. Which of the following force is responsible for the movement of the hammer?

(a) gravitational force alone

(b) electrostatic force alone

(c) magnetic force alone

(d) frictional force alone



3. During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is

(a) force of gravity.

(b) electrostatic force.

(c) the force of friction.

(d) magnetic force.


4. Fig.11.3 shows a container filled with water. Which of the following statements is correct about the pressure of water?

Soln:


 (a) The pressure at A > Pressure at B > Pressure at C.

(b) The pressure at A = Pressure at B = Pressure at C.

(c) The pressure at A <  Pressure at B > Pressure at C.

(d) The pressure at A <  Pressure at B.


5. Two objects repel each other. This repulsion could be due to

(a) frictional force only

(b) electrostatic force only

(c) magnetic force only

(d) either a magnetic or an electrostatic force


6. Which one of the following forces is a contact force?

(a) force of gravity

(b) force of friction

(c) magnetic force

(d) electrostatic force


7. A water tank has four taps fixed at points A, B, C, D as shown in Fig. 11.4. The water will flow out at the same pressure from taps at

(a) B and C

(b) A and B

(c) C and D

(d) A and C


8. A brick is kept in three different ways on a table as shown in Fig. 11.5. The pressure exerted by the brick on the table will be

(a) maximum in position A-C

(b) maximum in position B

(c) maximum in position

(d) equal in all cases.


Very Short Answer Questions

9. A ball of dough is rolled into a flat chapatti. Name the force exerted to change the shape of the dough.


10. Where do we apply a force while walking?


11. A girl is pushing a box towards the east direction. In which direction should her friend push the box so that it moves faster in the same direction?


12., In the circuit shown in Fig.11.6, when the key is closed, the compass needle placed in the matchbox deflects. Name the force which causes this deflection.

NCERT Exemplar Class 8 Science chapter 11 Solutions fig 5


13. During dry weather, clothes made of synthetic fibre often stick to the skin. Which type of force is responsible for this phenomenon?


14. While sieving grains, small pieces fall down. Which force pulls them down?


15. Does the force of gravity act on dust particles?



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