Physics Course/Force

Force is a physical quantity that describes the interaction between objects which can cause a change in an object’s motion or shape. In mechanics, a force can accelerate a mass, change its direction, or deform it. Force is a vector quantity, meaning it has both magnitude and direction. The SI unit of force is the newton (N), named after Sir Isaac Newton, who formulated the fundamental laws of motion.

In classical mechanics, force is commonly defined using Newton’s second law of motion:

F=ma

where:

• F is the force applied,
• m is the mass of the object,
• a is the acceleration produced.

This means that a force acting on a body changes its velocity, unless counteracted by another force.

• Vector quantity: Force has direction and magnitude.
• Contact vs. non-contact: Some forces act when objects physically touch (e.g., friction, tension), while others act at a distance (e.g., gravity, electromagnetic force).
• Can change motion or shape: Forces can accelerate, stop, or deform objects.

1. Gravitational Force The attractive force between any two masses, most noticeable between the Earth and objects on it. Expressed by Newton’s law of gravitation: F=Gr2m1​m2​​
2. Frictional Force A resistive force that opposes motion when two surfaces are in contact.
3. Normal Force The perpendicular contact force exerted by a surface to support the weight of an object.
4. Tension Force Force transmitted through a string, rope, or cable when it is pulled tight.
5. Electromagnetic Force Includes electric forces between charged particles and magnetic forces due to moving charges.
6. Applied Force Any external push or pull on an object.
7. Spring Force The restoring force exerted by an elastic object, such as a spring, following Hooke’s law: F=−kx