Lab Description
This is a general description of the
demonstration equipment. For detailed assembly information please go to the construction section.
The projectile motion lab consists of three
major components:
1. The launch ramp
2. The catcher
3. The control computer
Launch Ramp
The launch ramp consists of a track
approximately 1.2m long on a 45 degree angle suitable for rolling a ball
approximately 2.4cm in diameter. The bottom of the ramp is curved up via a
segment of plastic tubing in each rail, to a straight final segment 6cm long
that incorporates an optical speed sensor. This final segment is hinged at the
end point so that the launch angle can be adjusted. The adjustment is
accomplished by moving the entire ramp back and forth (mounted on a drawer
slide). The actuator and pulley arrangement that moves the ramp (plotter servo
controlled by the computer), is visible in the photo. The ball is held at the
top of the ramp until in a signal is received from the computer. This energizes
a solenoid that releases the ball. It rolls down the ramp, through the speed
sensor and off the end of the launcher.
Catcher
The catcher is a modified HP 7044A X-Y
plotter. As mentioned the Y axis servo was removed and used to drive the ramp angle
adjustment. The X axis servo was modified to drive a small cart on a track.
When the ball leaves the launch ramp the computer calculates where it will land
using the basic equations of motion described in the presentation
and moves the cart to that position.
Computer
There is a computer connected to the
demonstration equipment that performs a number of functions. The software to
perform these functions was written specifically for the demonstration in
Visual Basic (see Software). As mentioned, the computer controls the ramp
angle, releases the ball, measures the launch speed, calculates the range and
moves the cart to catch the ball. The input and output for these functions is
all done via the computer's parallel port. In addition to these functions the
computer program displays all of the initial conditions, launch parameters and
diagnostic data for each launch.