08. Class 8 Science Chapter 8 Force and Pressure
Welcome to Class 8 Science Chapter 8 Force and Pressure.
Force and Pressure – Exam Notes
Introduction
- In this chapter, we will learn about the concepts of force and pressure.
- We will explore how forces can change the state of motion of an object and affect its shape.
- We will also discuss various types of forces, both contact and non-contact forces, and their effects.
What is Force?
- Force is a push or a pull on an object.
- It can change the state of motion of an object, such as making it move, stop, or change direction.
- Force can also change the shape of an object.
Types of Forces
- Muscular Force
- Muscular Force is exerted by muscles when we push, pull, or lift objects.
- For example, when you lift a heavy bag, you are applying muscular force.
- Frictional Force
- Frictional Force opposes the relative motion of two surfaces in contact.
- For instance, when a car slows down, it’s due to the frictional force between the tires and the road.
- Magnetic Force
- Magnetic Force is the force of attraction or repulsion between magnets.
- When you bring two magnets close, you can feel them either attracting (if they have opposite poles) or repelling (if they have similar poles).
- Electrostatic Force
- Electrostatic Force is the force due to the attraction or repulsion of charged objects.
- When you rub a balloon against your hair and it sticks to the balloon, it’s because of electrostatic force.
- Gravitational Force
- Gravitational Force is the force of gravity that pulls objects towards the Earth.
- When you drop an object, it falls to the ground due to gravitational force.
Pressure
- Pressure is defined as the force per unit area.
- Mathematically, Pressure = Force / Area.
- If you apply the same force over a smaller area, it results in higher pressure.
Pressure in Liquids and Gases
- Both liquids and gases exert pressure on the walls of their containers.
- The pressure increases with the height of the liquid or gas column.
- For instance, the pressure at the bottom of a water column is higher than at the top.
Atmospheric Pressure
- Atmospheric pressure is the force exerted by the air around us.
- This pressure acts in all directions and helps balance the pressure inside our bodies.
- You can observe atmospheric pressure when a sucker sticks to a surface, and it’s due to the pressure of the air pushing on it from the outside.
Conclusion:
In conclusion, understanding the concepts of force and pressure is crucial in our daily lives. From lifting objects with muscular force to experiencing atmospheric pressure, these phenomena are all around us. By grasping these principles, we can better comprehend the physical world and its many interactions.
Keywords and Definitions
Important Definitions for Class 8 Science Chapter 8 Force and Pressure.
FAQ on Force and Pressure
1. What is force?
Answer: Force is a push or pull on an object, causing it to change its state of motion.
2. Can you provide examples of everyday forces?
Answer: Sure, common forces include pushing a door, kicking a ball, lifting a bag, or pulling a drawer.
3. What is the difference between contact and non-contact forces?
Answer: Contact forces involve physical touch, like friction or muscular force. Non-contact forces, such as magnetism or gravity, act at a distance.
4. How does a force affect the state of motion of an object?
Answer: A force can change the speed, direction, or shape of an object, or even all of these aspects.
5. What is pressure, and how is it related to force?
Answer: Pressure is the force exerted on a surface per unit area. It is calculated by dividing force by the area on which it acts.
6. Why do pointed objects exert more pressure than blunt ones?
Answer: Smaller area results in higher pressure for the same force. Pointed objects concentrate force on a smaller area, increasing pressure.
7. How does atmospheric pressure work?
Answer: Atmospheric pressure is the force exerted by the air around us. It acts in all directions and can be demonstrated using a rubber sucker.
8. Can you explain the concept of gravitational force?
Answer: Gravitational force is the attractive force between objects with mass. Earth’s gravity pulls objects towards its center.
9. What role does friction play in everyday life?
Answer: Friction opposes the motion of objects, leading to phenomena like the slowing down of a rolling ball or the stopping of a moving vehicle.
10. How does air exert pressure, and can we feel it?
Answer: Air exerts pressure on all surfaces it touches. We may not feel it in everyday situations, but it can be demonstrated using activities like the rubber sucker experiment.
Multiple Choice Questions (MCQs) on Force and Pressure
1. What is force?
a. A stationary object
b. A push or pull on an object
c. The speed of an object
d. The color of an object
Answer: b. A push or pull on an object
2. Which of the following is an example of a non-contact force?
a. Pushing a book
b. Magnetism
c. Lifting a bag
d. Pulling a drawer
Answer: b. Magnetism
3. How is pressure calculated?
a. Force multiplied by distance
b. Force divided by area
c. Area multiplied by distance
d. Mass divided by volume
Answer: b. Force divided by area
4. Why does a pointed object exert more pressure than a blunt one?
a. Pointed objects have more mass
b. Pointed objects have less force
c. Pointed objects concentrate force on a smaller area
d. Pointed objects have a larger surface area
Answer: c. Pointed objects concentrate force on a smaller area
5. What is atmospheric pressure?
a. Force exerted by the air around us
b. Force exerted by objects in the atmosphere
c. Force exerted by the sun
d. Force exerted by gravity
Answer: a. Force exerted by the air around us
6. Which force is responsible for the falling of objects towards the Earth?
a. Friction
b. Magnetism
c. Gravitational force
d. Tension
Answer: c. Gravitational force
7. What does friction do to the motion of objects?
a. Speeds it up
b. Slows it down
c. Has no effect on motion
d. Changes the direction of motion
Answer: b. Slows it down
8. In which direction does air pressure act?
a. Only upwards
b. Only downwards
c. In all directions
d. Only sideways
Answer: c. In all directions
9. What type of force is applied when you pull a rope?
a. Tension
b. Compression
c. Shear
d. Normal force
Answer: a. Tension
10. Which force is responsible for the feeling of weight?
a. Frictional force
b. Magnetic force
c. Gravitational force
d. Tension force
Answer: c. Gravitational force
This was the end of Class 8 Science Chapter 8 Force and Pressure.
For further information, refer to NCERT SOLUTIONS, NCERT NOTES, and NCERT BOOKS .
