Balanced forces

 

Balanced forces

When an object has two forces acting on it that are equal in size but opposite in direction, we say that the forces are balanced.

This is related to the First Law of Motion by Isaac Newton. This law says that an object will keep doing what it is doing, either staying still or moving with the same speed and direction, unless an unbalanced force changes its motion.

This means that if the forces on an object are balanced, the object will not change its speed or direction.

We can use a truck as an example to understand Newton’s first law:

 

 

Assuming that the forces acting on the truck are balanced:

 

• If the truck was originally moving, then it will continue to move in the same direction and speed.
• If the truck wasn’t originally moving, then it will stay still.

 

 

Force Diagrams

We can use arrows to show the direction and the size of the force on an object. This is called a force diagram.

 

 

The diagram above shows that the two arrows have the same length. This means that the cat has two forces that are equal (but in opposite directions).
The length of the arrow shows the size of the force. When the forces are balanced, the total force is zero. This total force is called the resultant force.

 

🔬 Knowledge Check: Balanced Forces

Test your understanding of how forces affect the motion of objects based on the lesson content.

1. If the forces acting on a stationary object are balanced, what will the object do?

• Start moving slowly
• Remain stationary (still)
• Change its direction

2. Which of the following describes 'unbalanced forces'?

• Forces that are equal in size and opposite in direction
• Forces that cause no change in an object's motion
• Forces that are not equal in size, causing a change in motion

3. If an object is moving at a constant speed in a straight line, what can we say about the forces acting on it?

• The forces are balanced
• The forces are unbalanced
• There are no forces acting on it at all

4. What is the 'resultant force' when two equal forces act on an object in opposite directions?

• The sum of the two forces
• Zero
• Double the size of one force

5. What three things can change when an unbalanced force acts on an object?

• Mass, weight, and volume
• Speed, direction, or shape
• Color, temperature, and density

Click to Reveal Answers

1. Remain stationary (Balanced forces do not change the state of rest).
2. Forces that are not equal in size (Unbalanced forces result in a net or resultant force).
3. The forces are balanced (Constant velocity implies no resultant force).
4. Zero (Opposite and equal forces cancel each other out).
5. Speed, direction, or shape (These are the physical effects of an unbalanced force).

 

Summary:

 

• Balanced forces occur when two forces applied to an object are equal in magnitude but opposite in direction.
• Isaac Newton’s First Law of Motion is closely related to the concept of balanced forces.