DEMONSTRATE AND EXPLAIN HOW THE MOTION OF AN OBJECT IS AFFECTED BY ONE OR MORE FORCES.

A STUDENT SHOULD KNOW THAT:

A. A BODY AT REST REMAINS AT REST; A BODY IN MOTION REMAINS IN UNIFORM MOTION
     UNLESS ACTED UPON BY AN EXTERNAL FORCE (NEWTON 'S FIRST LAW).

1. An object is said to be in uniform motion when it stands still or moves in a straight line at constant speed.
2. An object 's mass is the measure of its inertia.

B. WHEN MORE THAN ONE FORCE ACTS ON AN OBJECT AT THE SAME TIME, THE FORCES CAN 
     REINFORCE OR CANCEL EACH OTHER, PRODUCING A NET FORCE THAT WILL CHANGE THE
     SPEED AND/OR DIRECTION OF THE OBJECT.

1. Accelerated motion is defined as any change in motion and occurs when something speeds up, slows down, or changes direction.
2. The greater the force, the greater the acceleration.
3. Objects with a greater mass are harder to move than objects with less mass.

C. FRICTION IS A FORCE THAT CAN RETARD MOTION.

1. When friction is present, it must be overcome in order to start an object moving and/or to keep the object moving.

TO UNDERSTAND THE CONCEPTS OUTLINED ABOVE, A STUDENT SHOULD BE ABLE TO:

• Interpret a presentation of time/distance data to determine whether speed is steady or changing.
• Predict the motion of an object when one or more forces act upon it.
• Predict, based on data, how the force of friction will affect motion of a given object.
• Predict the motion of a moving object that is not being subjected to a net force.
• Design an experiment to investigate how the friction produced by surfaces of different textures affects motion of an object.