Learning Objectives

• Define force and the concept of net force.

• Explain the difference between balanced and unbalanced forces.

• Calculate the net force on an object from multiple forces.

• Describe how unbalanced forces change an object's motion.

Key Vocabulary

Force

A push or a pull on an object, capable of changing the object's state of motion.

Net Force

The total or overall force acting on an object, which determines how the object will move.

Newtons (N)

The standard unit of measurement for force in the International System of Units (SI).

Balanced Forces

Two forces acting in opposite directions on an object, and equal in size, creating a zero net force.

Unbalanced Forces

Forces that cause a change in the motion of an object because they are not equal and opposite.

What Are Forces?

• A force is a push or a pull acting on an object.

• Every force has a specific strength and a direction in which it acts.

• The standard unit used to measure the strength of a force is Newtons (N).

• Gravity and friction are common forces we experience on Earth every day.

Balanced vs. Unbalanced Forces

Balanced Forces

• Forces are equal in size and act in opposite directions on an object.

• The net force is zero (0 N), so all forces cancel each other out.

• There is no change in motion; the object is still or at a constant speed.

Unbalanced Forces

• Forces are unequal, which results in a change in the object's motion.

• The net force is greater than zero, causing the object to accelerate.

• The object will speed up, slow down, stop, or change its direction.

Calculating Net Force

Common Misconceptions About Forces

Summary

• A force is a push or pull measured in Newtons (N).

• Balanced forces have a net force of zero, causing no change in motion.

• Unbalanced forces have a net force greater than zero, causing a change in motion.

• Add forces in the same direction and subtract forces in opposite directions to find the net force.