PASCO ME-6800 Projectile Launcher (Short Range) - Manual (Page 33)

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M o d e l N o . M E - 6 8 0 0 E x p . 6 : C o n s e r v a t i o n o f M o m e n t u m
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• Since the tape does not produce the same inelastic collision each time, it is only useful to record this collision
once.
5. Use a plumb bob to locate on the paper the spot directly below the point of contact of the two balls. Mark this
spot on the paper as the “point-of-contact” spot. Carefully remove the carbon paper from the white paper.
Analysis
The time of flight for each shot is the same because the vertical distance for each shot is the same. Therefore, the
horizontal length of each path is proportional to the speed of the ball. Since the masses are the same, the horizontal
length of each path is also proportional to the momentum of the ball.
A. No Collision
1. Draw straight lines from the “point-of-contact” spot to each of the dots made by the ‘no collision’ shots.
2. Measure each straight line and record the length. Find the average of the five lengths and record the length as
the “initial x-momentum” in Table 6.1 and Table 6.2. (For example, if the length is 65 cm, record “65” as the
value for the “initial x-momentum” but do not include any units.)
B. Elastic Collision
1. Draw a straight line from the “point-of-contact” through the center of the group of dots made by the ‘no colli-
sion’ shots. (This is the center line from which all of the angles will be measured.)
2. Draw straight lines from the “point-of-contact” spot to each of the dots made by the ‘elastic collision’ shots.
(There should be five lines on each side of the center line.)
3. Measure from the “point-of-contact” to each of the dots made by Ball 1. Find the average of the five lengths.
Draw a straight line from the “point-of-contact” through the center of the group of dots made by Ball 1.
4. Measure the angle from the centerline to the straight line for Ball 1. Use this angle and the average length of
the line for Ball 1 to calculate the x-component for Ball 1 and the y-component for Ball 1. Record the values.
5. Measure from the “point-of-contact” to each of the dots made by Ball 2. Find the average of the five lengths.
Draw a straight line from the “point-of-contact” through the center of the group of dots made by Ball 2.
6. Measure the angle from the centerline to the straight line for Ball 2. Use this angle and the average length of
the line for Ball 2 to calculate the x-component for Ball 2 and the y-component for Ball 2. Record the values.
7. Add the x-momentum for Ball 1 and the x-momentum for Ball 2 and record the result in Table 6.1 as “Final
x-momentum”.
8. Calculate the initial kinetic energy of Ball 1 and the sum of the kinetic energy of Ball 1 and Ball 2 after the
collision.
9. Calculate the percent differences.
Table 6.1: Data for the Elastic Collisions
Item Value Item Value Percent difference
Initial x-momentum.
Ball 1
Final x-momentum,
Ball 1 + Ball 2
Final y-momentum,
Ball 1
Final y-momentum,
Ball 2
Initial kinetic energy,
Ball 1
Final kinetic energy,
Ball 1 + Ball 2