Kinematic Equations and Problem-Solving.pdf

Chap1-6 Kinematic Equations and Problem-Solving
1 The Kinematic Equations
The goal of this first unit of The Physics Classroom has been to
investigate the variety of means by which the motion of objects can be
described. The variety of representations which we have investigated
includes verbal representations, pictorial representations, numerical
representations, and graphical representations (position-time graphs and
velocity-time graphs). In Lesson 6, we will investigate the use of
equations to describe and represent the motion of objects. These equations
are known as kinematic equations.
There are a variety of quantities associated with the motion of objects
- displacement (and distance), velocity (and speed), acceleration, and
time. Knowledge of each of these quantities provides descriptive
information about an object's motion. For example, if a car is known to
move with a constant velocity of m/s, North for seconds for a
northward displacement of 264 meters, then the motion of the car is fully
described. And if a second car is known to accelerate from a rest position
with an eastward acceleration of m/s2 for a time of seconds,
providing a final velocity of 24 m/s, East and an eastward displacement
of 96 meters, then the motion of this car is fully described. These two
statements provide plete description of the motion of an object.
However, pleteness is not always known. It is often the case that
only a few parameters of an object's motion are known, while the rest are
unknown. For example as you approach the stoplight, you might know that
your car has a velocity of 22 m/s, East and is capable of a skidding
acceleration of m/s2, West. However you do not know the displacement
which your car would experience if you were to slam on your brakes and
skid to a stop; and you do not know the time required to skid to a stop.
In such an instance as this, the unknown parameters must be determine