Balanced and Unbalanced Forces – Lesson Summary

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Learning Objective

In this lesson we will learn about net force and compare balanced and unbalanced forces.

Learning Outcomes

By the end of this lesson you will be able to:

  • Explain how most objects have more than one force acting on them, with examples.
  • Define ‘net force’.
  • Calculate net force for objects experiencing multiple forces.
  • Explain what is meant by the term ‘balanced forces’, with examples.
  • Explain what is meant by the term ‘unbalanced forces’, with examples.
  • Compare the effect that balanced and unbalanced forces have on stationary objects and objects moving at a constant speed.
  • Describe how the magnitude of a net force and the mass of an object affect the rate of change of speed.

 
balanced and unbalanced forces lesson contents

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Lesson Topics

1 | Net Force

2 | Calculating Net Force

3 | Balanced Forces

4 | Unbalanced Forces

5 | Net Force, Mass and Acceleration

6 | Summary

Lesson Summary

  • Net force is the sum of all forces acting on an object.
  • Like individual forces, net force has both a magnitude and a direction.
  • If two forces are acting in the same direction, the magnitude of the net force is the sum of the two forces and the direction of the net force is the direction of the two forces.
  • If two forces are acting in opposite directions, the magnitude of the net force is the difference between the two forces and the direction of the net force is the direction of the larger force.
  • When two forces acting on an object are equal in magnitude and opposite in direction, they result in zero net force.
  • These forces are known as balanced forces.
  • Balanced forces do not affect the motion of an object.
  • If balanced forces are applied to a stationary object, the object will remain stationary.
  • If balanced forces are applied to a moving object, the object will continue moving at the same speed and in the same direction.
  • When two forces acting on an object are not equal in magnitude and opposite in direction, they do not result in zero net force.
  • These forces are known as unbalanced forces.
  • Unbalanced forces affect the motion of an object.
  • If unbalanced forces are applied to a stationary object, the object will begin moving.
  • If unbalanced forces are applied to a moving object, the object will change speed and/or direction.
  • When unbalanced forces are applied to an object, the rate that the object changes speed depends on the size of the net force and the mass of the object.
  • The greater the net force, the greater the rate of acceleration or deceleration.
  • The greater the mass, the less the rate of acceleration or deceleration.

 
balanced and unbalanced forces tower crane collapse

(Image: Angela McInnis, Wikimedia Commons)

(Header image: Andrii Zastrozhnov, Adobe Stock)