Bin Contents: a plumb bob, a clamp, a steel ball, a plastic rod, and a pair of goggles.

Obtain a ballistic pendulum apparatus – return when finished.

Note the pair of weights at the end of the pendulum; they tend to slip off so check them every time you do a trial in Part A.

The pendulum can be horizontal or vertical; for Part A it should be vertical, as shown; for Part B it should be either horizontal or removed.

Note the apparatus’s letter; the pendulum’s letter (not shown) ought to match; note also the green label specifies the effective pendulum length, L.

When the pendulum is vertical, the angle dial indicator can be slid into place..

The pin holds the pendulum to the apparatus; it’s easy to remove but tricky to re-insert.

The pendulum, removed from the apparatus.

Weigh the complete pendulum – this is a physical pendulum, its entire mass must be weighed.

To weigh the steel ball, place the yellow bin onto the scale …

… press the zero button to re-set the scale …

… insert the steel ball to obtain its mass.

When you remove the yellow bin, you will either get a negative value or an Err message, as shown, simply press the zero button again.

Plan Ahead – for Part B, obtain a carbon paper sheet from the same area you find the graph paper; we have various styles of carbon paper, they all work the same way; they all have a light and dark side; it’s the dark side that makes the marks.

Obtain two contiguous sheets of dot matrix paper (a box will be provided); make sure you do not separate these sheets; we want them to fold together.

Lay the carbon paper with the dark side down and the light side up (typically the light side looks blue not black; also, the light side doesn’t leave a mark).

Tape the carbon paper to the dot matrix paper’s seam.

Fold the dot matrix paper over the carbon paper as shown.

Draw a line across the center of the dot matrix paper as shown.

Verify that the carbon paper copied the line you just drew;; leave combo of papers aside, it will be used exclusively for Part B.

Plan Ahead – for Part B, we need to know the height from the floor to the point where the ball is launched. The best way to measure this is to set the apparatus as shown with the back end of the canon jetting out of the edge of the table.

Then, looking down the back of the cannon, measure the height from the floor to the center of the canon’s opening; note that there is a plastic ring at this end with a hole at the exact center of the canon’s shaft – this feature was not well photographed! – use that hole to better measure the height.

This is the “safest” end of the canon since nothing exists from it; nevertheless, wear the safety goggles!

Clamp the apparatus to the edge of the table more or less as shown; we need the clamp to ensure that the apparatus does not shift or wobble as the canon is fired.

Bring the pendulum to its vertical position and drop the angle dial until it stops; if the angle dial does not rest at zero, alert your instructor; this always means that the canon’s screws must be adjusted; the angle dial must be as close to zero as possible; 1/2 a degree off is the limit of how far it can be off.

Use the rod to press the steel ball into position; inside the canon is a spring loaded piston whose position is show by a yellow plastic indicator (see image below); ensure that the yellow indicator stops at the medium range setting AND that the balls stays against the piston and DOES NOT roll toward the front of the canon.

The tables are not necessarily level; if the ball doesn’t stay against the piston, turn the canon around or place it elsewhere on the table.

A close up of the canon’s side/top; the slits let you see where the piston (the yellow plastic) is located.

Notice the green string – pulling this string is how to fire the canon.

For Part A, when the canon is fired successfully, the ball enters AND stays inside the pendulum and the angle dial records the maximum angular displacement.

Note – observe how the pendulum is placed, it must be placed exactly as shown by the image; if it is not, the ball will not collide inellastically with the pendulum!

Again, if the experiment is successfully performed, the ball will be inside the pendulum.

If the ball doesn’t stick into the pendulum, first, check that the pendulum was attached properly to the apparatus, specifically, check that the orientation of the pendulum is exactly as shown; if the pendulum was attached the wrong / other way, this experiment will not work. If the pendulum is correctly attached but the ball continues to not stick inside, check that the canon is level and that the table is level, check other parts of the table, etc.

Use the lever to release the ball as shown.

To do Part B; after you calculated the “expected” range; measure the distance from the edge of the canon to the edge of the table, this is the “offset”. Subtract the “offset” from the “expected” to obtain the “adjusted”.

Use the plumb bob to find where the edge of the table is located over the floor.

Use tape to mark where the plumb bob actually touches the floor.

Note – for this to work the string needs to come out of the hole at the center of the top of the plumb bob; if your plumb bob doesn’t do that, alert your instructor!

A close-up showing how to use the tape to mark this location.

Set the zero end of a 2-m long stick against the paper..

We will use the 2-m long stick to measure the “adjusted” value; the “adjusted” value will be where the carbon paper you already prepared will be placed.

It’s not a bad idea to tape the end(s) of the stick to the floor….

Slide the carbon paper that you already prepared under the 2-m long stick in such a way that the line across the paper sits at your value for “adjusted”.

Tape the paper to the floor and remove the 2-m long stick.

Notice how this is going to work; when the ball is launched it will first travel across the “offset” distance just to get to the edge of the table, then, it will continue to project across the floor, a further “adjusted” distance until it hits the paper. The total horizontal distance the ball travels is the sum of “offset” and “adjusted” and by definition, “expected” = “offset” + “adjusted” (remember, you found “adjusted” by first calculating “expected” then subtracting “offset”, ie, “expected” – “offset” = “adjusted”)

Every time the ball hits the paper, write which trial number it corresponds too. The carbon paper will copy your note directly onto the paper below it.

Note – if your hits are spread too far or too wide, check that the ball stays against the piston and doesn’t roll away from it. If the ball rolls away from the piston and stays at the edge of the canon, it will not be launched properly.

The missed distance is found by measuring the location of the hit to the line that you drew; to find the actual or measured ranges: if the hit was over the line, ADD the miss distance to the “expected”; if the hit was under the line, SUBTRACT the miss distance from the “expected”..