PASCO ME-6831 Ballistic Pendulum_Projectile Launcher - Manual (Page 60)

B a l l i s t i c P e n d u l u m / P r o j e c t i l e L a u n c h e r T e a c h e r ’ s G u i d e
®
56 012-05375C
Calculations
• Use the equations given in the theory section for the approximate method.
Questions
1. The best other method of measuring velocity is described in the first part of experiment 1.
2. The greatest source of error is the equation used. This is an approximate equation, based on the assumption
that the masses involved are point masses. The amount of effect this equation has on the results will depend
on the exact geometry of the pendulum and ball, and should be between five and eight percent.
3. Typically, 70% of the kinetic energy of the ball is ‘lost’. It is not valid to assume that kinetic energy is con-
served.
Exp. 9: Projectile Motion—Exact Method
Procedure
1. The exact mass is not critical. Pick a value that gives a fairly large swing for best results.
2. With the steel ball and extra masses on the pendulum, the balance point will be somewhere on the ball catcher
itself. This makes it difficult to use string, but it is relatively easy to find the center of mass by balancing the
pendulum on a straightedge.
3. Measure this period as exactly as possible, using the smallest measurement angle that is practical.
4. The angle reached by the pendulum should not vary more than one degree between successive trials.
Calculations
• Use the equations given in the theory section for the approximate method.
Questions
1. The best other method of measuring velocity is described in the first part of experiment 1.
2. Sources of error include friction and measurement error.
3. Typically, 70% of the kinetic energy of the ball is ‘lost’. It is not value to assume that kinetic energy is con-
served.
4. The energy transfer is less efficient when there is a larger difference in the masses involved.
5. The exact method will give results that are typically within 2.5% of the actual value.