Newton's First Law
- Newton's laws of motion describe the relationship between the forces acting on an object and the motion of the object
- Newton's First Law states:
A body will remain at rest or move with constant velocity unless acted on by a resultant force
- A resultant force is required to change the motion of an object
- To speed up
- To slow down
- To change direction
- If the forces on a body are balanced (the resultant force is 0), the body must be:
- 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, other than friction, and it is moving at a constant velocity, what is the value of the frictional force F?