Resultant forces - Higher
When two or more forces act on an object, the resultant force can be found by adding up the individual forces.
A box on a table
If the weight of the box (acting downwards) is 50 N and the normal reaction force (acting upwards) is 50 N, the forces are balanced. The resultant force is zero.
An object falling through the air
If the weight of the box (acting downwards) is 50 N and the air resistance (acting upwards) is 20 N, the forces are unbalanced. The resultant force is 30 N downwards.