4.2 Newton’s First LawChapter 4: Forces and the Laws of Motion

Inertia

Misconception: an object with no force will be at rest.

Inertia – the tendency of an object to maintain its state of motion, or tendency not to accelerate.

Acceleration is determined by net external force. Net external force – to

total force from a combination of external forces on an object; sometimes called the resultant force.

Vector sum of all forces acting on an object.

Mass is a measurement of inertia. Inertia is proportional to mass.

Objects in motion tend to stay in motion.

Equilibrium

Equilibrium – the state in which there is no change in a body’s motion. Occurs when there is no net force on the

object.▪ When the vector sum of all forces acting on

an object is equal to zero.0 F