Balanced and unbalanced force

• Determining the resultant force

  1. When forces act in the same direction: Resultant force, F = Sum of forces

  2. When forces act in opposite directions: Resultant force, F = Sum of forces

  3. When opposing forces are equal: Resultant force = 0 N
• If forces act on an object and the resultant force is zero, the object will either remain at rest or continue moving at constant speed and in the same direction
• When forces are not balanced, the object will experience a resultant force
• For a moving object, if the resultant force is zero, it will continue moving at constant speed and in the same direction
• For an object at rest, if the resultant force is zero, it will remain at rest
• When forces are balanced, the object will not experience a resultant force
• Almost without exception, there is more than one force acting on an object, the combination of all the forces acting on the object is called the resultant force
• If the forces are not balanced, the object will experience a resultant force
• Forces acting on an object can be in the same direction. They may also be acting from different direction(s)
• When two or more forces act on an object, the resultant force can be found by adding up the individual forces
• As the apple is NOT moving, the resultant force on it must be zero
• Objects with unbalanced forces acting on it will either speed up or slow down
• Object will either speed up or slow down due to the resultant force
• The effect(s) experienced by the object will depend on this resultant force
• Non-Contact Forces


  • Forces that do not require direct contact between two objects e.g. gravitational force, magnetic force
• We can represent the forces acting on an object using arrows. The arrow shows the direction of the force acting in. The length of the arrow represents the magnitude (size) of the forces
• There are two forces: the desk pushes up on the apple and gravity pulls downward on the apple
• Contact Forces

  • Forces that depend on contact between two objects e.g. normal contact force, friction
• Gravity is the force that pulls on the apple
• Objects with balanced forces acting on it will have no change in its state of rest or motion