IB Physics SL

Revision Notes

2.2.2 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, other than friction, and it is moving at a constant velocity, what is the value of the frictional force F?

WE - Newtons first law question image, downloadable AS & A Level Physics revision notes

WE - Newtons first law answer image, downloadable AS & A Level Physics revision notes

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