Lesson Plan

State Newton's first law of motion in both of its parts (rest and motion)

Explain how friction accounts for everyday objects slowing to a stop, and name the types of friction

Apply F_net = 0 to a body moving at constant velocity, balancing applied force against friction

Identify the system of interest and distinguish external from internal forces in a worked situation

Describe inertia and explain how it is related to mass

Distinguish mass from weight and explain why mass is independent of gravity

4.2

"A body at rest tends to remain at rest. A body in motion tends to remain in motion at a constant velocity unless acted on by a net external force." "Generally, friction is an external force that acts opposite to the direction of relative motion or to prevent slipping." "According to Newton's first law of motion, any object moving at constant velocity has no net external force acting upon it, which means that the sum of the forces acting on the object must be zero." "The force of friction depends on two factors: the coefficient of friction and the normal force." "Inertia is the tendency for an object at rest to remain at rest, or for a moving object to remain in motion in a straight line with constant speed. ... the inertia of an object is proportional to the mass of the object." "Mass is a measure of the amount of matter (or stuff) in an object. ... Unlike weight (which changes if the gravitational force changes), mass does not depend on gravity. The mass of an object is the same on Earth, in orbit, or on the surface of the moon."