Physics (Combined)

Physics

# Forces and their Interactions

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Forces and their Interactions

Vector and Scalar Quantities

**Scalar quantities**are entirely described by a magnitude (size) only.- Examples of scalar quantities include speed, distance, mass, temperature and energy.
**Vector quantities**have both a magnitude and a direction.- Examples of vector quantities are force, velocity, displacement, acceleration and momentum.

Newton's First Law of Motion

- The
**first law of motion**states that an object will remain at rest or continue in a straight line at a constant speed unless acted upon by an external force. - This property of resistance to change in motion is known as
**inertia**.

Newton's Second Law of Motion

- According to Newton's
**second law of motion**, force is the product of mass and acceleration. It's expressed as F = ma. - The
**acceleration**of an object is directly proportional to the net force acting on it and inversely proportional to its mass. - The unit of force in the International System of units is the
**Newton**(N) which is defined as 1 kg·m/s².

Newton's Third Law of Motion

- Newton's
**third law motion**states that for every action, there is an equal and opposite reaction. - This means that any force exerted onto a body will create a
**force of equal magnitude**but in the opposite direction on the object that exerted the first force.

Principles of Forces

**Friction**is a force that opposes motion. It occurs when two surfaces are in contact with each other.- Air resistance is a type of friction that acts on objects moving through the air.
- The force of gravity near the Earth's surface is referred to as
**weight**and is equal to an object's mass multiplied by the acceleration due to gravity. **Centripetal force**is the force that keeps a body moving with a uniform speed along a circular path and it's directed along the radius towards the centre.- The
**equilibrium**of forces occurs when the sum of forces acting on a body is zero, resulting in no change in motion.

Momentum

- Momentum is a
**vector quantity**defined as the product of an object's mass and velocity. - The principle of
**conservation of momentum**states that the total momentum before and after a closed, isolated system interaction remains the same.