Class 8 Science - Chapter Force and Pressure NCERT Solutions | Give two examples of situations in which

Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.

An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the following terms:

muscular, contact, non-contact, gravity, friction, shape, attraction

(a) To stretch the bow, the archer applies a force that causes a change in its ——.
(b) The force applied by the archer to stretch the bow is an example of ——— force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a ———— force.
(d) While the arrow moves towards its target, the forces acting on it are due to ———— and that due to ———— of air.

A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.

An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to

(a) pressure of water
(b) gravity of the earth
(c) shape of rubber bulb
(d) atmospheric pressure

Fill in the blanks in the following statements:
(a) To draw water from a well we have to ——— at the rope.
(b) A charged body ———— an uncharged body towards it.
(c) To move a loaded trolley we have to ———— it.
(d) The north pole of a magnet ———— the north pole of another magnet.

Give two examples each of situations in which you push or pull to change the state of motion of objects.

A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

In the following situations identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.

(a) Squeezing a piece of lemon between the fingers to extract its juice.
(b) Taking out paste from a toothpaste tube.
(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
(d) An athlete making a high jump to clear the bar at a certain height.

Which of the following can be beaten into thin sheets?
  (a) Zinc     (b) Phosphorus     (c) Sulphur     (d) Oxygen

Fill in the blanks
(a) Most liquids that conduct electricity are solutions of , ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the terminal of the battery.
(d) The process of depositing a layer ofany desired metal on another material by means of electricity is called .

Fill in the blanks:
(a) Friction opposes the _____________ between the surfaces in contact with each other.
(b) Friction depends on the _____________ of surfaces.                                                                                                                                                                      (c) Friction produces __________.
(d) Sprinkling of powder on the carrom board ________ friction.
(e) Sliding friction is ___________ than the static friction.

List conditions under which combustion can take place.

Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have one-celled body. (T/F)
(b) Muscle cells are branched. (T/F)
(c) The basic living unit of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)

Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.

Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called                  .
(b) Species found only in a particular area is known as                          .
(c) Migratory birds fly to far away places because of                     changes.

Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.

What are the different ways in which water gets contaminated ?

Explain the importance of reproduction in organisms.

Describe the construction of a kaleidoscope.

Describe with the help of a diagram an instrument which can be used to detect a charged body.

Sketch larynx and explain its function in your own words.

Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Clear, transparent water is always fit for drinking. Comment.

Make a labelled diagram of a candle flame.

Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement.

(a) Rolling, static, sliding
(b) Rolling, sliding, static
(c) Static, sliding, rolling
(d) Sliding, static, rolling

Complete the cross-word puzzle using the hints given below

Across
    1. The process of the fusion of the gametes.
    6. The type of fertilization in hen.
    7. The term used for bulges observed on the sides of the body of Hydra.
    8. Eggs are produced here.

Down
    2. Sperms are produced in these male reproductive organs.
    3. Another term for the fertilized egg.
    4. These animals lay eggs.
    5. A type of fission in amoeba.

What is metamorphosis? Give examples.

Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?