# Monkey and Hunter

From the National STEM Learning Centre, this short video illustrates the effect of gravity on a projectile's motion by using a classic physics demonstration called the Monkey and the Hunter. If a hunter fires horizontally at a monkey in a tree, and simultaneously the monkey releases their grip to fall off the tree, will the bullet hit the monkey? One version of the video is aimed at teachers and shows how to set up the demonstration. The other version can be used with students in place of the demonstration.

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### Stuart BillingtonThu, 2011-01-13 20:38

Things I like:

They're short and straight to the point.
"Teachers" one highlights likely areas where it can all go wrong.
They're visually and very clearly shows the setup and the equipment, in situ (especially important for the "teachers" one).
It has some humour -- especially of the type that reassures, rather than being irrelevant.
It is located in a very nice and yet realistic-for-a-state-school lab. It's light and airy and modern and white/clean/new.
"Class" one's explanation cuts straight the the heart of the matter and doesn't muddy the water with anything unnecessary or off-on-a-tangent. Basically, it does exactly what it says on the tin; no more, no less.
High quality -- much better than anything else I've seen.

For the "class" video, a niggle: It is not a simple thing to assume that the perpendicular components of motion are independent of each other. A-level study of projectile motion must introduce this notion (and perhaps justify it with appeal to Newton's Laws), and it is deep. The monkey and hunter demo exists primarily to reinforce this very claim in a visual and memorable way. In your voice-over you talk (2:30ish mark) as if the result shouldn't be surprising given that the horizontal and vertical components are independent, whereas, in fact, it is counter-intuitive to a lot of people and it is good evidence for believing that the components are independent.

I turn the tin around so that the open end is facing the gun. I cover this end in tissue paper (held on with an elastic band around the opening) and draw the monkey on that. I then fire a ball-bearing at it (using an elastic band setup -- it has to be against a wall and safety is more important!) at a higher speed. The effect is that the ball bearing pierces the tissue and gets trapped inside the tin -- the monkey really does get shot. It's easier to see that the monkey has been shot, in the absence of the slow motion video, as the tin rattles at the end.

I might also reassure people that the rather impressive electromagnet is not required -- I use a tiny little thing (and am now very jealous of yours!) -- and that, regardless, it shouldn't be switched on until ready to fire, as the wires all get very hot very quickly (unless you're wiring it up some way that I'm not , in which case, please share!).

### aurwinSun, 2011-01-16 18:10

Loved the large scale and the simple foil strip trigger. How about following up the old Nuffield constant head beaker to rubber tube under the old ticker time arm to give parabolic stream of water drops which can then be illuminated with a strobe? http://www.practicalphysics.org/go/Experiment_417.html

### asoberSat, 2011-01-29 13:31

Wow! This is the best demo and video I have seen so far! Absolutely awesome! What a great way to learn about vertical and horizontal components of velocity. Very useful the graphics used in the video to trace the path of the monkey and bullet.
A master class video!

### Carol DavenportThu, 2011-02-03 11:10

Excellent use of slow motion photography. Thank you.

### Alom ShahaFri, 2011-02-04 20:51

The slow motion video was captured using a digital SLR - which you or one of your colleagues may have, so you could also do this at school.

### jjsandersonMon, 2011-02-07 10:38

To clarify Alom's comment about the high-speed filming: lots of cameras out there, including many digital SLRs, will record at 60 frames/sec. That's not really 'high-speed,' though - you get more of a dreamlike look than anything useful for gathering data.

The sequence in these films was shot at 300 frames/sec with a Casio camera (an EX-F1, if anyone's counting). Several Casio Exilim cameras will shoot at high speeds, and aren't half bad for the money. That said, they need *lots* of light to do a decent job.

### sannyThu, 2011-09-15 13:43

This is so beautifuly simple and yet so amazingly effective!!! Well done on the slow motion video of the entire motion!! I love it! Thanks.

### FstrthnthspdflghtFri, 2012-03-09 10:49

Thank you so much for doing this experiment so well - it'll be a good one to show my students to get them thinking.

### Ronaldo GCThu, 2016-12-01 01:53

Such a great demo on gravity and projectile. Huge thanks!