In this experiment you will study motion with constant velocity,
motion with constant acceleration, elastic and inelastice collisions
and simple harmonic motion
(
).
You will study one dimensional motion using
an air-track system to reduce the effects of
air resistance. To study ,
you will study the behaviour of a simple pendulum.
Ordinarily, it is difficult to examine motion with constant acceleration, since objects in free fall tend to move too rapidly, and frictional forces tend to arise in most everyday situations. These factors hinder a direct observation of the underlying physical principles of motion, and in fact this is one of the reasons why these principles were poorly understood until Galileo's famous experiments. In this lab, it will be possible to study motion in the absence of almost any friction by using a rider on a ``frictionless" air-track. The air-track has rows of small air jets running down its side, which support the rider on a thin film of air and allow it to float just above the track. When the track is level and the rider is given a slight push, it will move with constant velocity; when the track is slightly inclined, the rider will experience a small acceleration due to the component of gravity which is parallel to the track.
To study the motion of the rider, you will also need to be able to make accurate measurements of its position at given intervals of time. For this you will use a sonar device called the Sonic Ranger. This apparatus sends out discrete pulses of sound waves, which are reflected back by the object or objects under observation. The sensor is the essentially the same as used in some commercially available autofocus cameras. The Sonic Ranger is in turn connected to a computer, which calculates the distance to the object based on the time it takes the signal to leave the sonar module and return. If a series of such measurements is made in rapid succession, then the computer can reconstruct the motion of the rider over some time interval, and this information can be used for many other calculations, such as the ``instantaneous'' velocity or acceleration of the rider as a function of time. An essential part of this lab is becoming familiar with using the computer to acquire and analyze data. Use of the computer offers many advantages over manipulating data by hand, but you can benefit from it only if you have learned how to use the computer effectively and understand its limitations.
Figure 2.1:
Schematic view of Sonic Ranger with air track.