Measure the length of the pendulum from the pivot point to the center of
the ball cavity.
Measure
the mass of the pendulum.
Measure the mass of the projectile.
For the remainder of the experiment, cock the gun until the spring is at the long-range setting.
B. Determination of Pendulum Velocity and the Initial Velocity of the Projectile
M = combined mass of pendulum cup and ball,
L = length of pendulum, and
V = velocity after impact.
Using the conservation of energy,
Return the pendulum to the vertical position. Make sure the angular protractor mounted
on the support is properly zeroed.
Fire the gun five times and record the rise of the pendulum after each shot as measured
by the angle on the protractor. Remember to read the scale to 1/10 th of the smallest
division.
Use a spreadsheet to record the angles and to calculate the velocity after the collision
using the conservation of energy for each shot.
The momentum, P, is defined as the product of mass and velocity, and is a quantity we
will devote a chapter to later on. The momentum of ball and holder after the collision is
P_{after} = MV. The momentum before the impact is that of just the ball since only
the ball is moving: P_{before} = m_{ball}v_{0}, where v_{0}
is the initial velocity of the ball. The law of conservation of momentum tells us that P_{after}
= P_{before }so that
v_{0} = MV/m_{ball}.
Calculate v_{0} for each shot and then calculate the average with a 90%
confidence interval.