The Elements Projectile Motion and the Principle of Conservation of Momentum – Lab Report Example

The paper “The Elements Projectile Motion and the Principle of Conservation of Momentum" is a potent example of a lab report on physics. This law-the principle of conservation of momentum states that a system of two or more bodies is not being acted on by any external forces does not experience any change in momentum (Dean S. Edmonds 31-32). It aims at determining the projectile’s initial velocity by means of the ballistic pendulum and measurements of the projectile’s vertical distance and range of fall. The experiment expects that the results obtained through the two methods will agree. The theory being investigated concerns the momentum of a body-the product of the velocity of a body and its mass.

Method
This experiment uses the apparatus, which is a combination of a spring gun and a ballistic pendulum. The pendulum is made up of a huge cylindrical bob that has been hollowed out to be able to handle the projectile. The projectile in itself is made up of a brass ball, which is fired into the suspended pendulum bob. In order to indicate the height of the Center of gravity, of the loaded pendulum, a brass index is embedded on the pendulum bob. The apparatus used in this experiment include 

1. Triple-beam balance
2. Ballistic pendulum
3. 2-m stick
4. -in. plate
5. Carbon paper
6. Level
7. 1-m stick
8. Metric steel scale
9. Plumb bob
10. White paper and masking tape

First, the initial projectile velocity is obtained by measuring the range and fall. It is worth noting that, at this stage, the pendulum is not used. The ball is then fired horizontally, severally, such that it strikes a target set on the floor and the exact spot that the ball hits is approximated (33). The range for each shot is measured; this represents the horizontal distance. The vertical distance of the ball is then measured by measuring the ball’s vertical fall using the meter stick. It should be noted that the distance is measured from the bottom of the ball and not the center since it is the ball’s bottom that hits the floor. The pendulum is then allowed to swing freely, and the brass ball is fired into the pendulum bob, when it is at rest, causing it to swing with the ball embedded in it. This is repeated several times-four time-and the pendulum’s position is recorded. The average value of the position of the pendulum on the rack is then computed. With the pendulum set in close correspondence to the average value calculated, the vertical distance h1 from the index point attached to the pendulum to the base of the apparatus is measured. Additionally, the vertical distance h2 is measured from the index point to the apparatus base when the pendulum is at its lowest position. The weight of the pendulum and that of the ball are weighed separately and their values recorded (34).

Results
The horizontal distance from the plumb bob ark to the firing pin was measured and recorded as 0.33. The average horizontal range x recorded is 2.6948, which had an average error of 0.00003. This error may be as a result of the apparatus moving on the bench between shots, or the apparatus was not being placed near the edge of a level table. From the experiment, the vertical distance y, of the fall was measured and recorded as 0.943m. The reading of the curved scale-the highest point of the ballistic pendulum-was measured five times and averaged; it was recorded as 20.6cm. The average height, of the center of gravity of the pendulum-vertical distance, h1, when it is at its highest position-was measured and recorded as 20.6cm. The height of the pendulum’s center of gravity when it is on its lowest position, vertical distance h2 was recorded as 10.30cm. The distance through which the pendulum’s center of gravity was raised, vertical distance h, was recorded as 10.30cm. The velocity of projection, V, from fall and range measurements was calculated and recorded as 6.146m/s. the mass of the ball and the pendulum bob were separately measured and recorded as 56.7g and 198.8g respectively. The ball’s velocity before the collision was calculated and recorded as 6.15m/s while that of the pendulum and the ball immediately after the collision was calculated and recorded as 1.4m/s. The difference between the velocity of projection from fall and range, 6.146m/s and that of the ball before the collision, 6.15m/s, is 0.04m/s. this represents a 0.65 percentage difference.