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NCERT Class 8 Exercise and Solutions of Chapter 11 Force and Pressure

Orchid International School acknowledges the importance of Class 8 Science Chapter 11 and the pivotal role that NCERT Solutions for this chapter play in helping students excel in their examinations. Our NCERT Solutions for Class 8 Science Chapter 11, "Forces and Pressure," have been meticulously crafted by professional and experienced educators to provide students with a valuable resource for achieving outstanding marks.

Force and Pressure

Question 1 :

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

 

Answer :

 The following are the required examples-

Push force examples: 

  1. A toy car is at rest and is moved by applying a push force.

  2. We move a bicycle by pushing it.

Pull force examples include:

  1. Taking out a drawer.

  2. Drawing water from a well by pulling a rope.

 

 


Question 2 :

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

 

Answer :

The following are two instances of situations in which a force can modify the shape of an object:

  1. When plastic bottles are squeezed, they change shape.

  2. A rubber band's shape changes when it is stretched.

 


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 either push or pull 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, noncontact, gravity, friction, shape, attraction 

  1. To stretch the bow, the archer applies a force that causes a change in its _______. 

  2. The force applied by the archer to stretch the bow is an example of ________ force.

  3.  The type of force responsible for a change in the state of motion of the arrow is an example of a _______ force. 

  4.  While the arrow moves towards its target, the forces acting on it are due to _____ and that due to _____ of air.

 

Answer :

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

  2. The force applied by the archer to stretch the bow is an example of muscular force. 

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

  4. 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) . When squeezing a lemon, the hands exert muscular force on the fruit. As a result, the lemon's form shifts.

(b) .The hand exerts muscular strain on the tubing of the syringe. As a result of the toothpaste, the tube's shape changes.

(c) .A downward force is applied to the spring by the suspended weight. The spring lengthens as a result of this.

(d) .When attempting a high leap, an athlete's feet exert muscular power on the ground. As a result, he leaps over the bar, changing his state of motion.

 

 


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 :

A blacksmith hammers a molten iron piece. He imparts a massive compressive force to the iron, causing it to alter shape.

 


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 :

 An inflated balloon becomes charged when it is rubbed against a wall after being rubbed with synthetic fabric. The balloon attaches to the wall because a charged body attracts an uncharged body. The electrostatic force is the force that exists between the charged balloon and the wall.

 


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 :

The muscular force applied by the hand and the weight owing to gravity are the forces operating on the plastic bucket. Because these two forces are equal and opposite one another, there is no change in the state of motion.

 


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 :

The force of gravity/weight and friction caused by the earth's atmosphere are the two forces that act on the rocket shortly after launch.

 

 


Question 10 :

When we press the bulb of a dropper with its nozzle kept in water, the 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) the gravity of the earth

(c) the shape of a rubber bulb 

(d) Atmospheric pressure

 

Answer :

(d) Atmospheric pressure. When air escapes from the dropper's nozzle, it creates a pressure difference, which causes water to be pulled into the nozzle.


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