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Chapter Analysis
Intermediate19 pages • EnglishQuick Summary
The chapter on 'Force and Pressure' introduces the concept of force as a push or pull, resulting from interactions between objects. It explores different types of forces, including contact and non-contact forces, and examines how forces can change the motion or shape of objects. The chapter also delves into the concept of pressure, defining it as force per unit area, and discusses the effects of pressure in solids, liquids, and gases.
Key Topics
- •Push and pull as forces
- •Interaction and force
- •Contact and non-contact forces
- •Effects of force on motion
- •Pressure and its calculation
- •Pressure in fluids
- •Atmospheric pressure
- •Applications of pressure in daily life
Learning Objectives
- ✓Understand the concept of force as a push or pull resulting from interaction
- ✓Differentiate between contact and non-contact forces
- ✓Analyze how forces can change the motion or shape of objects
- ✓Explain the concept of pressure and its application in fluids
- ✓Describe the effects of atmospheric pressure
- ✓Identify real-life applications and implications of pressure
Questions in Chapter
Give two examples each of situations in which you push or pull to change the state of motion of objects.
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Give two examples of situations in which applied force causes a change in the shape of an object.
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Fill in the blanks in the following statements.
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 push it. (d) The north pole of a magnet repels the north pole of another magnet.
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An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target.
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 a 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.
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Identify the agent exerting the force and the object on which it acts in the following situations.
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A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?
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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.
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Name the forces acting on a plastic bucket containing water held above ground level in your hand.
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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.
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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
Answer: (a) pressure of water. (b) gravity of the earth. (c) shape of rubber bulb. (d) atmospheric pressure.
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Additional Practice Questions
Explain how friction affects the motion of a rolling ball.
mediumAnswer: Friction opposes the motion of the rolling ball. It acts in the opposite direction to the ball's movement and gradually reduces its speed until the ball comes to rest.
How does pressure relate to force and area?
easyAnswer: Pressure is defined as the force exerted per unit area. It is expressed mathematically as pressure = force / area. Therefore, the smaller the area on which a force acts, the larger the pressure.
Discuss the differences between contact and non-contact forces.
mediumAnswer: Contact forces require physical contact between the objects involved, such as friction and muscular force. Non-contact forces act at a distance without direct physical contact, such as gravitational, magnetic, and electrostatic forces.
Why are sharp tools more effective for cutting compared to blunt tools?
mediumAnswer: Sharp tools concentrate force over a smaller area, resulting in higher pressure, which makes it easier to cut through materials.
Describe an experiment to demonstrate atmospheric pressure.
hardAnswer: One way to demonstrate atmospheric pressure is by using a rubber sucker. Press the sucker onto a smooth surface and notice how it sticks due to atmospheric pressure, requiring significant force to remove it.
Explain with an example how force can change the shape of an object.
easyAnswer: Pressing a lump of dough on a plate changes its shape due to the force applied. Similarly, when you stretch a rubber band, the force changes its shape.
Why do porters place a round piece of cloth on their heads when carrying heavy loads?
easyAnswer: Porters use a round piece of cloth to increase the area of contact between the load and their head, which reduces the pressure exerted, making it easier to carry the load.
Consider a scenario where two equal forces act on opposite sides of an object. What is the net force acting on it?
easyAnswer: When two equal forces act on opposite sides of an object, they cancel each other out, resulting in a net force of zero, meaning there is no change in the object's state of motion.
How do non-contact forces affect objects without touch?
mediumAnswer: Non-contact forces, such as gravity, magnets, and electrostatic forces, apply force from a distance. For example, gravity pulls objects toward each other without any physical contact.
NCERT Exemplar
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