5.2 - Newton's 1st & 2nd Laws

Newton's First Law - Resultant force changes motion

• Newton's First Law - If the resultant force on an object is zero, its velocity doesn't change:
  • A stationary object stays stationary.
  • A moving object continues at the same velocity (same speed and direction).
• When an object is stationary or moving at a constant velocity, the forces on it are balanced.
• Velocity only changes if the forces are unbalanced, giving a non-zero resultant force that causes an acceleration in the direction of the force.

A non-zero resultant force can cause an object to:

• start moving
• stop moving
• speed up
• slow down
• change direction