NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure

NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure are given below. Here we have provided the best and error-free answers to all the exercise questions that will strengthen your foundation in science. Solving NCERT questions will assist you in grasping the content in the Crop Production and Management chapter in a better way.

In these solutions, we have answered all the intext and exercise questions provided in NCERT class 8 science textbook. NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free or can read them online.

Force and Pressure Class 8 Science NCERT Solutions

Exercise Questions

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

Answer: Two examples of push force are as follows:

(i) A heavy box at rest is pushed to move it from one room to another. This changes the state of motion of the box.

(ii) A player pushes a football using his foot. This changes the state of motion of the ball.

Two examples of pull force are as follows:

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

(ii) A drawer is pulled to open it. This changes the state of motion of the drawer

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

Answer: The forces which change the shape of an object are as follows:

(i) By pressing the clay between the hands, it deforms.
(ii) The shape of the plastic bottle changes by squeezing it.

Question 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.

Answer: (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 pull or push it.

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

Question 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:

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

Answer: (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.

Question 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.

Answer: (a) In squeezing a piece of lemon, we make use of muscular force to extract its juice. This muscular force acts on the lemon. As a result, the shape of the lemon gets changed.

(b) We use our muscular force to take out paste from a toothpaste tube. The muscular force acts on the toothpaste tube. As a result, the shape of the tube gets changed.

(c) Here, the suspended load exerts a force on the spring and pushes the spring downwards. As a result, the spring gets stretched. Hence, its shape gets changed.

(d) An athlete pushes the ground with his feet. His feet exert a muscular force on the ground. This allows him to jump over the bar. As a result, his state of motion gets changed.

Question 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: The force due to hammering causes the change in the shape of the iron and iron can be moulded in the shape of the required tool.

Question 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: On rubbing an inflated balloon with a piece of synthetic cloth, it becomes charged. A charged body attracts an uncharged body. When this charged 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.

Question 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: Forces acting on bucket are as follows:
(i) Muscular force of arms acting upward.
(ii) Force of gravity acting downward.

Both the forces do not bring any change in the state of motion because both of them are acting in equal and opposite directions and thus they cancel each other’s effect.

Question 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.

Answer: Two forces acting on the rocket immediately after leaving the launching pad are:

• Frictional force due to air.
• Force of gravity pulling in downward direction.

Question 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 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