Force and Pressure 8 Science — Revision Notes
Force is a push or pull that can change the motion or shape of an object. Pressure is the force applied per unit area and has important applications in dai
TL;DR: Force is a push or pull that can change the motion or shape of an object. Pressure is the force applied per unit area and has important applications i…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Force is a push or pull that can change the motion or shape of an object. Pressure is the force applied per unit area and has important applications in dai
Concept of Force
- Force is a push or pull exerted on an object
- Forces can change the speed, direction, or shape of an object
- Contact forces require physical contact; non-contact forces act at a distance
- Weight is the force exerted by gravity on an object
- Friction is a force that opposes motion between surfaces
Pressure Definition and Formula
- Pressure is force applied perpendicular to a surface divided by the area
- Formula: Pressure = Force / Area
- Unit of pressure is Pascal (Pa) in SI system
- Pressure depends on both force and area of contact
Pressure in Solids
- Pressure in solids acts perpendicular to the surface
- Sharper objects exert greater pressure with the same force due to smaller area
- Demonstration: needle point creates more pressure than blunt end with same force
- Skiing on snow uses wide skis to reduce pressure and prevent sinking
Pressure in Fluids
- Fluids include liquids and gases that can flow
- Pressure in fluids acts in all directions equally
- Atmospheric pressure is the weight of air above us at sea level
- Water pressure increases with depth due to weight of water above
- Buoyancy is the upward force exerted by fluids on submerged objects
Applications of Pressure
- Hydraulic systems use fluid pressure to multiply force in machines
- Syringes use pressure differences to draw and expel fluids
- Vacuum cleaners work by creating pressure difference
- Suckers use pressure difference to create adhesion
Key Terms
- Force: A push or pull that can change motion or shape of an object
- Pressure: Force per unit area exerted on a surface
- Friction: Force that opposes motion between two surfaces in contact
- Buoyancy: Upward force exerted by a fluid on a submerged or floating object
Frequently Asked Questions
Why do we use sharp objects like knives instead of blunt ones?
Sharp objects have smaller contact area, so they exert greater pressure on the object being cut, making them more effective.
Why do we feel more pressure the deeper we go in water?
Water pressure increases with depth because the weight of water above increases, exerting more force on objects below.
More 8 Science Revision Notes
- Crop Production and Management
- Microorganisms: Friend and Foe
- Cell: Structure and Functions
- Reproduction in Animals
- Sound
- Chemical Effects of Electric Current
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