## Topic outline

• ### Force and Pressure

##### Q1. Fill in the blanks.

i.        To draw water from a well we have to pull at the rope.

ii.        A charged body attracts an uncharged body towards it.

iii.        To move a loaded trolley we have to push or pull it.

iv.        The north pole of a magnet repels the north pole of another magnet.

v.        The atmospheric pressure is due to the weight of air present in the atmosphere above us.

vi.        Force has magnitude as well as direction.

vii.        Liquids exert equal pressure at the same depth.

viii.        Liquids and gases exert pressure on the walls of their containers.

##### Q2. True/False

i.        Air exerts pressure in all directions. True

ii.        The north pole of a magnet attracts the north pole of another magnet. False

iii.        The pressure exerted by a liquid depends on the area of base of its container. True

iv.        To draw water 'from a well, we have to apply push force at the rope. False

v.        A force arises due to the interaction between two objects. True

vi.        The strength of a force is usually expressed by its magnitude. True

##### Q3. What is the unit of force?

Ans. Newton

##### Q4. Give one example where force moves a stationary object.

Ans. Pushing a chair

##### Q5. Give one example where force stops a moving object.

Ans. A fielder stopping a ball

##### Q6. What is force?

Ans. A push or a pull on an object is called a force.

##### Q7. Does liquid exert pressure in all directions?

Ans. Yes, Liquid exerts pressure in all directions.

##### Q8. Why does the shape of tooth paste tube change when we squeeze it?

Ans. The shape changes because our finger applies force on the tube.

##### Q9. What can bring change in state of motion of an object?

Ans. A force may bring a change in the state of motion of an object.

##### Q10. Which force can be used to gather iron pins scattered on the floor?

Ans. Magnetic force can be used to gather iron pins scattered on the floor.

##### Q11. Which force do the animals apply while moving, chewing and doing other activities?

Ans. Muscular force

##### Q12. Which force is responsible for raising our body hair when we try to take off a terylene or polyester shirt in the dry weather?

Ans. Electrostatic force

##### Q13. Write one example where force changes the speed of a moving object.

Ans. Speed of moving a rubber tyre or a ring increases whenever it is pushed.

##### Q14. Why does a boat come to rest when we stop rowing it?

Ans. Friction between water and the boat brings it to a stop once we stop rowing.

##### Q15. Write any two application of atmospheric pressure in our everyday life.

Ans. Drinking straw and Dropper work on the existence of atmospheric pressure.

##### Q16. Explain why, snow shoes stop you from sinking into snow.

Ans. The snow shoes have large, flat soles so they exert less on the soft snow and stop the wearer from sinking into it.

##### Q17. What happens to the springs fixed to the seat of a bicycle when we sit on it?

Ans. When we sit on the seat of a bicycle, the force exerted by the body weight compresses the spring and changes its shape.

##### Q18. Give one practical application of magnetic force.

Ans. The closing of door of refrigerator works on the application of magnetic forces.

##### Q19. Give one example from daily life where force changes the shape of an object.

Ans. Example: The shape of dough changes on pressing with a rolling pin to make chapatis.