Physics
Force
Forces in Nature
Class 11
⚡ Quick Summary
There are four fundamental forces in nature: Gravity, Electromagnetism, the Weak Nuclear Force, and the Strong Nuclear Force. They each have different strengths and ranges.
No specific formulas given in the excerpt.
- Gravitational Force: The force of attraction between any two objects with mass. It is the weakest of the four forces but has an infinite range.
- Electromagnetic Force: The force between charged particles. It is much stronger than gravity and also has an infinite range. It can be attractive or repulsive.
- Weak Nuclear Force: Responsible for radioactive decay. It is weaker than both the electromagnetic and strong nuclear forces and has a very short range.
- Strong Nuclear Force: The strongest force, responsible for holding the nucleus of an atom together. It has a very short range.
Action and Reaction (Newton's Third Law)
Class 11
⚡ Quick Summary
For every action, there's an equal and opposite reaction. This means if you push something, it pushes back on you with the same amount of force, but in the opposite direction. Crucially, these forces act on *different* objects.
F<sub>action</sub> = -F<sub>reaction</sub>
- Action and reaction forces always act on two different objects.
- They have equal magnitudes.
- They have opposite directions.
- The resultant of action and reaction forces is NOT zero *because they act on different objects.* If the object of interest is, say, the object being acted *upon*, we only consider the force acting *on* that object.