# 4.4.1 Newton’s First Law

### Newton's First Law

• Newton’s First Law states:

A body will remain at rest or move with constant velocity unless acted on by a resultant force

• If the forces on a body are balanced (the resultant force is 0), the body must be either:
• At rest
• Moving at a constant velocity
• Since force is a vector, it is easier to split the forces into horizontal and vertical forces
• If the forces are balanced:
• The forces to the left = the forces to the right
• The forces up = the forces down
• The resultant force is the single force obtained by combining all the forces on the body

#### Worked Example

If there are no external forces acting on the car and it is moving at constant velocity, what is the value of the frictional force F?   ### Author: Ashika

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.
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