Force and Pressure Class 8 Science Chapter 8 Notes are available here. These notes were carefully prepared by our team of subject experts to make it easier for you to grasp the concepts. We hope you like these notes and have a great time studying with them.
Force and Pressure Class 8 Science Chapter 8 Notes
Force:
- Force is a “push” or a “pull” exerted on an object.
- Motion is caused by the application of force.
- Force can be measured in units such as Newtons (N).
- Forces can act in different ways, including gravitational, electromagnetic, and frictional forces.
- Forces can change the speed, direction, or shape of an object.
- Forces are described by vectors, which include magnitude and direction.
- Understanding forces is crucial for studying the behaviour of objects in motion.
- Forces can be balanced or unbalanced, affecting an object’s motion differently.
- Forces have practical applications in engineering, physics, and everyday life.
Force is generated due to interaction:
- Force is generated through interactions between objects.
- The application of force causes displacement in the direction of the applied force.
- Force requires two objects to interact with each other.
- Interactions between objects result in the creation of a force between them.
- Forces acting in the same direction on an object add to each other.
- When two forces act in opposite directions on an object, the net force is the difference between the two forces.
- The strength of a force is typically expressed by its magnitude.
- The magnitude of a force can be larger, smaller, or equal to another force.
- Changes in the direction or magnitude of an applied force result in different effects.
- If two forces of equal magnitude act in opposite directions on an object, the net force on the object is zero.
Force can Change the State of Motion:
- Force has the ability to alter the state of motion of an object.
- Application of force can change the speed of an object.
- If the force is in the same direction as the object’s motion, it increases the object’s speed.
- Conversely, if the force is in the opposite direction to the object’s motion, it decreases the object’s speed.
- Any change in an object’s speed or direction of motion is considered a change in its state of motion.
- Forces can bring about changes in the state of motion of an object.
- The state of motion of an object is characterised by its speed and direction of motion.
- The state of rest is defined as the state of zero speed.
- An object can be in a state of rest or in motion, both of which are considered states of motion.
- It is important to note that the application of force may not always result in a change in the state of motion.
Force can lead to change in shape:
- Force can cause a change in the shape of an object.
- An object requires the application of force to change its shape.
- An object cannot change its shape on its own.
- Objects cannot move, change speed, change direction, or change shape without the influence of an external force.
- Force is required to induce any kind of change in an object’s properties or behaviour.
- Changes in an object’s shape can be a result of external forces acting upon it.
- Force plays a crucial role in altering the physical characteristics of objects, including their shape.
Contact Forces
Muscular Force
- Muscular force is generated by the action of muscles in the human body.
- It enables us to perform movements and bending actions.
- Animals also utilise muscular force for various physical activities and tasks.
- Examples of animals using muscular force include bullocks, horses, donkeys, and camels.
- Muscular force is a contact force, meaning it can only be exerted when in direct contact with an object.
Friction
- Friction is a force that changes the state of motion of objects.
- The force of friction acts on moving objects and opposes their motion.
- The direction of the frictional force is always opposite to the direction of motion.
- Friction arises from the contact between surfaces.
- Friction is an example of a contact force as it requires direct contact between objects to come into play.
Non-Contact Forces
- Attraction or repulsion between objects is an example of a non-contact force.
- Objects can exert forces on each other without physical contact.
Magnetic Force
- Magnets can exert forces on other objects without direct contact.
- The force exerted by a magnet on a piece of iron is an example of a non-contact force.
Electrostatic Force
- The force exerted by a charged body on another charged or uncharged body.
- It occurs between bodies that are not in physical contact.
- Electrostatic force is an example of a non-contact force.
Gravitational Force
- It is an attractive force that acts on all objects.
- Gravity pulls objects towards the Earth.
- Every object in the universe exerts a gravitational force on every other object.
Pressure
- Pressure is defined as the force applied per unit area.
- Pressure is calculated by considering the forces acting perpendicular to the surface.
- The formula for pressure is pressure = force / area.
- When the same force is applied over a smaller area, the pressure exerted on the surface is greater.
- Gases and liquids exert pressure on the walls of their containers.
- The pressure exerted by gases and liquids is due to the collisions of their particles with the container walls.
- The pressure of a gas increases with an increase in temperature or an increase in the number of gas particles.
- Pressure plays a significant role in various phenomena, such as fluid dynamics, hydraulic systems, and atmospheric pressure.
Atmospheric Pressure
- The atmosphere is the air envelope surrounding the Earth.
- The pressure exerted by the air in the atmosphere is called atmospheric pressure.
- Atmospheric pressure is the force exerted by the weight of the air due to gravity.
- The force of gravity acting on the air molecules creates atmospheric pressure.
- Atmospheric pressure decreases with increasing altitude because the density of air decreases.
- Atmospheric pressure is commonly measured using a device called a barometer.
- Changes in atmospheric pressure can indicate weather conditions, such as high or low-pressure systems.
- Atmospheric pressure is essential for various natural phenomena, such as wind patterns and the water cycle.
- It also plays a role in human activities, such as aviation and weather forecasting.