- After having an apple fall on his head one day, Sir Isaac Newton came up with 3 fundamental laws that are very important when calculating and researching physics.
Newton's 1st Law
"If an object has no forces acting upon it, it will keep it's velocity and direction."
- This means that if an object has no forces acting on it then it will either stay still or continue in the same velocity and direction that it was already moving.
- This means a body will continue to be the same state it was in before as long as the forces acting on it are balanced; so when the resultant force is zero.
- This rule only really applies in given examples or in a vacuum, as objects constantly have forces acting on them on Earth.
- When the resultant force on an object is equal to zero, that object is said to be in equilibrium.
- There are several types of equilibrium, such as translational, rotational and thermal equilibrium.
- Likewise, when the resultant force on an object is not zero, then it is in disequilibrium.
Newton's 2nd Law
"The acceleration of
- Newton's second law states that the resultant force on an object can be found by multiplying its mass and acceleration.
- Therefore:
ΣF = ma
- The unit for force is called Newtons, denoted by N and named after Isaac Newton himself.
- The acceleration is in the same direction as the resultant force on the object.
Newton's 3rd Law
"Every force has an equal and opposite reaction"
- This means that any force applied is met by an equal force facing the opposite direction.
- When body A exerts a force on body B, body B exerts an equal and opposite force on body A.
- For example if you punch a wall with a force of 20 newtons, then the wall hits you back with 20 newtons.
- Another example could be a book on a table. If the book weighs 10 newtons, then it would have to be pushed up by a force of 10 newtons by the table.