A force is an interaction that causes an object to [[Acceleration|accelerate]], change direction, or deform. Force is a [[Vector|vector]] quantity. The SI unit of force is the **Newton (N)**, where **1 N = 1 kg·m/s²**. According to Newton’s Second Law of Motion, force is defined as: $F=ma$ Where: - $F$ = force (N) - $m$ = [[Mass|mass]] of the object (kg) - $m$ = acceleration (m/s$^2$) Forces can be categorized into two main types: 1. **Contact Forces** – Forces that act through physical contact: - **Frictional force** (resists [[General Motion|motion]]) - **Tension force** (in ropes or strings) - **Normal force** (perpendicular support force) - **Applied force** (pushes or pulls by objects or people) 2. **Non-Contact (Field) Forces** – Forces that act at a [[Distance|distance]]: - **Gravitational force** (due to [[Gravity|gravity]]) - **Electromagnetic force** (between [[Electrical Charge|charged]] particles) - **Nuclear forces** (strong and weak interactions in [[Atom|atomic]] nuclei) **Newton’s Laws and Force** - **First Law**: An object remains at rest or in uniform motion unless acted upon by an external force. - **Second Law**: Force equals mass times acceleration . - **Third Law**: For every action, there is an equal and opposite reaction.