Unit 01 -- Inertia and Constant Motion

Vocabulary

1. Inertia -- the resistance to changes in motion. The amount of this resistance is based on the amount of mass in the object, because each atom resists a change in its motion. The more atoms, the more total resistance to a change in motion.
2. Force -- an interaction between objects that attempts to cause a change in motion. In other words, a push or a pull.
3. Scalar Quantity -- a measurement that does not take a direction, e.g. time or temperature.
4. Vector Quantity -- a measurement that requires both a magnitude (size) and a direction, e.g. force or displacement.
5. Vector -- an arrow drawn to represent a vector quantity. The length of the arrow shows the relative magnitude of the measurement. The direction in which the arrow points is the direction in which the vector quantity is acting.
6. Vector Addition -- a method that uses geometry to add two vector quantities of similar type.
7. Resultant -- the vector result of the combination of two or more vectors through vector addition.
8. Net Force -- the vector sum or resultant force remaining after all forces acting on an object are added using vector addition.
9. Law of Inertia -- also known as Newton's first law of motion. It states that every object continues in a state of rest or of uniform speed in a straight line unless acted upon by a net force.
10. Mechanical Equilibrium -- sometimes called translational equilibrium. It is the state of an object or system of objects for which there are no changes in motion.
11. Equilibrium Rule -- for an object or system of objects to be in mechanical equilibrium -- in other words, for them to remain at rest or for their motions to be constant -- the sum of all the forces acting on an object must be zero. Another way of saying this is that objects that do not experience changes to their motion of any kind have no net force acting on them.
12. Distance -- the total amount of length traveled in any direction. This is a scalar quantity.
13. Displacement -- a measure of an object's change in position -- including both a length measurement and a direction. This is a vector quantity.
14. Speed -- the distance traveled in a unit of time. It answers the question "how fast..." It is a scalar quantity.
15. Instantaneous Speed -- the speed at a particular moment in time. This is what is seen on the speedometer of your car.
16. Average Speed -- the speed over a period of time. This the result your get when you divide the total distance traveled by the total time it takes to travel that distance. Note that it does not tell you exactly what speeds were traveled during that period, but simply gives you an average.
17. Velocity -- the speed traveled in a direction. Because it requires a direction, this is a vector quantity.
18. Constant Velocity -- the state in which neither the speed nor the direction of motion changes.

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