Chapter 10, Section 1 The Nature of Force Monday, March 8, 2010 Pages

Objectives  Explain how balanced and unbalanced forces are related to motion.  State Newton’s First Law of Motion.  Define inertia.

Vocabulary Words  Force  Net force  Unbalanced force  Balanced forces  Inertia

What is Force?  In science, force is either a PUSH or PULL.  The net force is the overall force on an object after all the forces are added together.  When there is net force acting on an object, the forces are unbalanced.

Unbalanced Force Same Direction  When 2 forces act in the same direction, the net force is the sum of the two individual forces.  Unbalanced forces can cause an object to start moving, stop moving, or change direction (accelerate).  In this example, the object will move to the right.

Unbalanced Forces Opposite Directions  When forces act in opposite directions, the net force is the difference between the two forces.  In this example, the object moves to the left.

Balanced Forces Opposite Directions  When two equal forces act in opposite directions, they cancel each other out.  Balanced forces acting on an object will not change the object’s motion.  In this example, the object doesn’t move.

Newton’s First Law of Motion  An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an unbalanced force.  Also called the Law of Inertia.  Inertia is the tendency of an object to resist change in its motion.

What is Mass?  Mass is the amount of matter in an object.  The SI unit of mass is the kilogram (kg).  The amount of inertia an object has depends on its mass.  The greater the mass of an object, the greater its inertia.  Mass can also be defined as a measure of the inertia of an object.

Homework  Workbook 10.1 (3/11)  Vocabulary quiz 10.1 (3/11)