Force, Mass, and Gravity

Force  

- Force is a vector quantity: it has both magnitude and direction.  

- It is defined as a push or pull acting on an object.  

- Measured in newtons (N).  

- In mechanics, forces are often treated as acting at a single point (a particle) which occupies a single position in space.  

Types of Forces  

- Weight: The effect of mass under gravity; it always acts vertically downwards.  

- Tension: A pulling force; always acts away from the object.  

- Thrust: A pushing force; always acts towards the object.  

- Friction: A resistive force; always acts to oppose motion.  

- Reaction Force: Produced by surfaces; always acts perpendicular to the surface.  

Mass  

- Mass is a measure of the amount of matter in an object.  

- It is a scalar quantity, measured in kilograms (kg).  

- Mass is universal and does not change with location.  

Gravity  

- Gravity is the force by which a body (e.g., planet or star) pulls objects towards its centre.  

- The acceleration due to gravity (g) is measured in m/s².  

- On Earth, g approx 9.81 m/s^2, often approximated as 10 m/s^2.  

- The exact value of g varies with location and is different elsewhere in the universe.  

Weight  

- Weight is the product of mass and gravitational acceleration:  

  W = m x g 

- It is a force, measured in newtons (N).  

- Weight is a vector quantity: it always acts vertically downwards.  

- Unlike mass, weight varies with location because g changes.