PASCO ME-6815 PROJECTILE CATCHER ACCESSORY - Manual (Page 12)

Projectile Catcher Accessory 012-05091E
8
Alternate Method: Determining the Muzzle Velocity with Photogates
1. Attach the Photogate Bracket to the launcher and attach two Photogates to the bracket.
Plug the Photogates into a computer or other timer.
2. Put the ball into the Projectile Launcher and cock it to the long range position.
3. Run the timing program and set it to measure the time between the ball blocking the two
Photogates.
4. Shoot the ball three times and take the average of these times. Record in Table 1.2.
5. Use a distance of 10 cm (between the Photogates) to calculate the initial speed. Record the
initial speed in Table 1.2 and Table 1.4.
1
Time
2
3
Trial Number
Average Time
Initial Speed
Table 1.2: Initial Speed Using Photogates
Part II: Ballistic Pendulum
Set Up
1. Find the masses of the ball and catcher. Record in Table 1.3.
2. Suspend the ball catcher as a pendulum, as explained in the general instructions.
3. With the Projectile Launcher mounted as in Figure 1.1, clamp the suspended ball catcher
directly in front of the muzzle.
4. Attach a thread to the ball catcher and string it through the Velcro assembly (see the
general instructions) on the base of the Launcher.
Procedure
1. Load the Launcher (set to long range) with the steel ball. Fire a test shot to see how far out
the thread is pulled. Pull a few centimeters of the thread back through the Velcro, leaving
the rest of the thread slack between the Launcher and the catcher. When the ball is shot
into the pendulum again, the thread will become taut just before the catcher reaches its
maximum height. This reduces the effect of friction on the thread.
2. Fire the ball into the pendulum five times. After each trial, pull the pendulum back until the
thread is taut and measure the height above the level of the muzzle to which the pendulum
swung. Record in Table 1.3.