In this experiment we will use a ballistic pendulum to determine the initial horizontal launch velocity of a brass ball. The first method will use horizontal projectile motion while the second method will use conservation of momentum and conservation of energy. At NO time during the experiment are you to adjust the spring gun's tension.
In the first part of the experiment you will carefully displace the pendulum so that you can use the spring gun to project the brass ball as a horizontal projectile. By measuring the ball's range and height of release you will be able to calculate the ball's flight time and its muzzle velocity.
In the second part of the experiment you will fire the brass ball from the spring gun into the pendulum which will swing up and be caught at its highest displacement. This inelastic collision initially conserves momentum while the pendulum's swing conserves energy. You will then be able to once again calculate the ball's release velocity. A percent difference between the two values for the ball's release velocity will conclude your calculations.
In addition to the ballistic pendulum, you will need the following equipment:
- 1 triple beam balance
- 1 meter stick
- carbon paper
- plumb line
- target paper
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Part I As shown in the top picture above, carefully secure the pendulum out of the path of the ball. Test fire the spring gun and note where the brass ball strikes the floor then place your target paper and carbon paper near the anticipated point of contact. Use a plumb line to record the location of the edge of the table on the floor. After firing the gun more five times, measure and record each of the ball's impact positions. Remember to always make sure that the base of the pendulum is flush with the edge of the desk before each firing. When you are finished, fold up your target paper and place the names of your group members on the outside. This paper must be turned in to your instructor.
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Part II Mass the ball and then, as shown in the picture below, carefully move the pendulum so that it is now directly in the ball's line of fire. Measure and record the height of the screw on the side of the pendulum's cup. You will now fire the ball five times into the catcher, each time recording the height that the pendulum's cup recoils.
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equilibrum position |
recoil height |
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recoil height |
Δ height |
trial |
(cm) |
(cm) |
Analysis
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When you have completed this lab, make sure that you submit your results online as well as turn in your calculations and target paper. Names are important!