# NCERT Solutions Class 8 Science Force and Pressure

NCERT Solutions for Class 8 Science for chapter 11 Force and Pressure

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

Examples of Push:

(i) A suitcase at rest is pushed  to move  from one place to another. This changes  the state of motion of the suitcase.

(ii) A football is pushed  by a player using  his foot. This changes  the state of motion of the football.

Examples of Pull:

(i)  To open  a drawer, it is pulled  out. This changes the state of motion of the drawer.

(ii) Rope is pulled  to draw water from a well. This changes  the state of motion of the water bucket.

2. Give two examples of situations in which applied force causes a change in the shape of an object.

(i) Squeezing of tin container.
(ii) Pressing clay by hands.

3. 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.

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

(b)    A charged body  attracts an uncharged body  towards it.

(c)    To move  a loaded  trolley we have  to  either push orpull it.

(d)    The north pole of a magnet  repels the north pole of another magnet.

4. 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 of muscular, contact, non-contact, gravity, friction, shape, attraction, etc.

(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)    To stretch the bow, the archer applies  a force that causes a change  in its  shape.

(b)    The force applied by the archer to stretch the bow is an example of  muscular force.

(c)    The type of force responsible for a change  in the state of motion of the arrow is an example of a contact force.

(d)    While  the arrow moves  towards its target, the forces acting on it are due to  gravity and that due to friction of air.

5. 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.

(a)    Muscular force is used in squeezing a piece of lemon. This muscular force acts on the lemon. Thus, the shape  of the lemon gets changed.

(b)    To take out paste from a toothpaste tube, muscular force is used and it acts on the toothpaste tube. Thus, the shape  of the tube gets changed.

(c)    The suspended load exerts a force on the spring and pushes  the spring in downward direction. Thus, the spring gets stretched and its shape  gets changed.

(d)    In a high  jump, an athlete pushes  the ground with his feet and exerts a muscular force on the ground. As a result, he can jump over the bar. Thus, his state of motion gets changed.

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

Answer: A blacksmith uses muscular force when  he hammers on a hot piece of iron. Due to this muscular force, the shape  of the iron gets changed and iron piece can be given  a desired shape.

7. 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?

Answer: An inflated balloon gets charged when  it is rubbed with a piece of synthetic cloth. A charged body  attracts an uncharged body. When  this balloon is pressed against a wall, it sticks to the wall. The force acting between the charged balloon and the wall  is the electrostatic force due to which  it was stuck.

8. 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.

Answer: When  we hold  a plastic bucket filled  with water above  the ground, there are two forces act on it. First is the gravitational force which  acts downwards and second  is the muscular force exerted by us which  acts in the upward direction. The two forces are equal  in magnitude but  opposite in direction. Hence, the net force on the bucket is zero. Therefore, there is no change  in its state of motion.

9. 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.

(i) The force of gravity which  tries to pull  the rocket downwards.

(ii) The force of friction due to earth’s atmosphere, which  opposes  the motion of the rocket.

10. 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 dropp 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.

Answer: The correct option is (d).

Explanation: When  the air filled  in the nozzle  is removed, the atmospheric pressure, which  is acting on the water, forces the water to fill  the nozzle  of the dropper.

## Latest CBSE News

• The Central Board of Secondary Education (CBSE) has decided to drop some of the chapters from the class 10th Social Science book.  As per the new curriculum, the three chapters of political studies and two environmental texts are not included in the CBSE board examinations. However, these chapters are still teach in the classes. They are just separate from the CBSE board examinations.  Download...
• If you’re the one who opted for the medical stream because you liked studying biology. Unfortunately, you have been unable to clear the NEET exam and now worried about their future. Actually, most people think that career options for PCB end at medical. Today in this article we will be talking about some of the career options for PCB stream which students can pursue after class 12th. Here is the...
• As soon as the Central Board of Secondary Education (CBSE) result dates coming closer, rumours are also on the peak of its level. All the suppositions are meaningless because the board officials confirmed the declaration date of class 10th and class 12th results. This year CBSE class 10th and class 12th exams have started in the month of February and ended in the Ist week of April. As per the...
• While the long-standing standards for picking streams in our nation have settled that toppers and tutorially-skilled undergrads normally float towards science, it's pursued being toppled. Undergrads, today, are proactively picking the business stream, regardless of their scholarly standing. In this way, in case you're needing to pick your stream once you are done with tenth, or have just settled...
• Board exams play a very important role in our lives. It boosts our knowledge and also helps to know our status in academic life. Both class 10th and class 12th play a very significant role in a student’s life.It also helps inselecting the stream of their own choice. So that in later, they can’t regret their decisions. Board exams are key factors in determining the course of student’s careers....
• As it is the beginning of a new school year, every 11th class CBSE passed student is eager and making plans on how to score the best in their class 12th CBSE boards. It definitely is a good start to reach their goal of scoring 90+ percentages in the exams. Students who have opted for the science stream often get very stressed upon how they are going to perform, let me tell you something…scoring a...
• We all know CBSE has conducted every year board exams for class 10. As soon as we land in class 10, everyone starts suggesting different things. They tell us to study hard because this is the first step towards your career. If you are willing to take science stream in class 11th and 12th, then it is very important to get good marks in class 10. So that you can easily take your stream. Check out...