Balanced forces are when two forces that are applied onto an object are both equal but opposite.
Isaac Newton’s first law states that to every action, there is always an equal and opposite reaction. Newton’s first law is particularly related to balanced forces. It also states that if an object is at rest and the forces acting on it are balanced then the object will remain at rest.
Let’s look at Newton’s first law using a lorry as an example:
So, as seen in the diagram, let’s say that the forces acting on the lorry are balanced.
1. If the lorry was originally moving, then it will continue to move in the same direction and at the same speed.
2. If the lorry was not moving, then it will remain stationary.
In this example, the two opposing forces are thrust and friction. Friction is a force that resists the motion of surfaces sliding across each other. The roughness from the two surfaces (between the wheels and the ground) means the two surfaces cannot move past each other easily.
Another example is with boats in water
A boat floats due to the upthrust (also known as buoyancy) of the water being equal to the weight of the boat.
This concept is illustrated in the diagram below – Take into account buoyancy is the upward force that is exerted by a fluid that opposes the weight of a partially or fully immersed object.
The best way to represent this is by using force diagrams.
(hint: arrows are very important)
The arrows on a force diagram tell us the direction of the force and size of the force.
As you can see in the diagram above, the two arrows are the same size. This tells us that the forces acting on the book are equal (but opposite). The bigger the arrow size, the greater the force. When forces are balanced, we can say that the overall force is zero. The overall force is known as the resultant force.