Higher tier: Balanced forces
What are forces?
A force is a push or a pull.
Contact forces arise between two objects which are in contact.
A force that opposes or prevents movement and converts kinetic energy into heat. is an example of a contact force.
Non-contact forces act between two objects which are not in contact.
The force of gravity and magnet force are examples of non-contact forces.
Calculations involving forces
The resultant A push or a pull. The unit of force is the newton (N). is the single force that has the same effect as two or more forces acting together.
Two forces in the same direction
Two forces that act in the same direction produce a resultant force that is larger than either individual force.
You can easily calculate the resultant force of two forces that act in a straight line in the same direction by adding their sizes together.
Example
Two forces, 3 N and 2 N, act to the right. Calculate the resultant force.
Resultant force F = 3 N + 2 N = 5 N to the right.
The resultant force is 5 N to the right.
Two forces in opposite directions
Two forces that act in opposite directions produce a The single force that could replace all the forces acting on an object, found by adding these together. If all the forces are balanced, the resultant force is zero. that is smaller than either individual force.
To find the resultant force subtract the magnitude of the smaller force from the magnitude of the larger force.
The direction of the resultant force is in the same direction as the larger force.
Example
A force of 5 N acts to the right, and a force of 3 N act to the left.
Calculate the resultant force.
Resultant force F
Resultant force F = 5 N - 3 N = 2 N to the right.
The resultant force is 2 N to the right.
