PHYS 121
Name:_______________________Box #:______
Date:_____________  Afternoon   Evening
Lab Activity Report
___/25    
ballistic pendulum
(autumn 2013)

Other members of your lab group (up to 3 total including yourself)

____________________________ ____________________________

procedure:

  1. Latch the pendulum at 90° so it is out of the way, then load the projectile launcher. Select a "range" (short, medium, long) and use it for the rest of the experiment. Allow the pendulum to hang freely and move the angle indicator to 0°.

  2. Fire the launcher and record the angle reached. You can adjust angle by changing the mass of the pendulum. Find a convenient angle.

  3. Measure the mass of the ball, m, and the mass of the pendulum and ball together, M.

  4. Determine the center of mass of the pendulum and ball. This can be done by suspending the pendulum by a loop of string and adjusting it until it balances. Measure the distance from the pivot to the center of mass, R.

  5. Load the launcher. Set the angle indicator a few degrees less than it would normally reach.

  6. Fire the launcher and record the angle. Repeat!

results:

What "range" have you selected? _______________________

M
(g)
m
(g)
R
(cm)
   

Record the angle for several trials:

nθ
(°)
1 
2 
3 
4 
5 
6 
average 




Compute the muzzle velocity of the ball?









 

Since the muzzle velocity of the ball is quite low, another way to determine the muzzle velocity of the ball is to measure the horizontal distance for the ball to strike the floor.

Derive an equation for the initial muzzle velocity, assuming it is horizontal, in terms of the initial height, y0, above the floor and the horizontal distance to impact, x.











 

The initial height of the ball above the floor, y0 = _______________ (m)

nx
(m)
1 
2 
3 
4 
5 
6 
average 

Compute the initial muzzle velocity from the average x.





 





Compare this value with the value you obtained from the ballistic pendulum. Which is larger? What is the percent difference?







 

The ball sometimes rolls forward in the launcher instead of resting against the spring. What effect does this have on the muzzle velocity?









 

What relevant suggestions do you have that might improve the results of this lab activity?









 

revised 8 Oct 13