A. Initial Measurements
- Measure the length of the pendulum from the pivot point to the center of
the ball cavity.
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
- 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
Pafter = MV. The momentum before the impact is that of just the ball since only
the ball is moving: Pbefore = mballv0, where v0
is the initial velocity of the ball. The law of conservation of momentum tells us that Pafter
= Pbefore so that
v0 = MV/mball.
Calculate v0 for each shot and then calculate the average with a 90%