Average speed: the speed over an OVERALL journey.
Does NOT mean normal or common. Involves math.
Instantaneous speed: the speed of the moment.
Does NOT mean fast speed.
Average Speed and Instantaneous speed are BOTH calculated using the SAME equation - speed = distance/time. They BOTH have to do with the time it takes someone to travel a certain distance.
Newton's First - unbalanced forces cause acceleration.
An object at rest DOES have forces acting on it.
Newton's 2nd - Describes the relationship between force, acceleration, and mass. It is represented by the equation F=MA
Newton's 3rd - When two objects interact along a line, the reaction is equal and opposite. For these paired objects, every action has an equal and opposite reaction.
Inertia - the TENDENCY for an object to resist acceleration. A quantitative measurement of inertia is MASS - recorded in numbers and given the unit grams or kilograms.
An object's mass is NOT dependent on the speed of the object - as such, an object's inertia is not dependent on speed or acceleration, since these are the same ideas.
Acceleration - any change in speed AND/OR direction.
A car traveling 50 mph along a straight highway is not accelerating - why?
A car traveling a long a curved race track is accelerating - why?
Friction - a FORCE that opposes motion between two objects when they touch.
Gravitational force are attractive and depend on the masses of the objects and the distances between them.