General Question

Harp's avatar

Hammer flipping mystery (see details)

Asked by Harp (19142points) July 15th, 2008

If you hold a regular claw hammer out in front of you so that the face of the hammer points to your left and the claw to your right, then you toss the hammer up (without imparting any spin) so that the handle does one complete revolution around the head of the hammer before you catch it again, you’ll find that the face now points to your right and the claw to your left. Why?

It obviously has to do with the difference in mass between the two sides of the hammer, but I can’t recall enough of my physics to explain what’s going on here.

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43 Answers

waterskier2007's avatar

well i believe that it is simply that the differences in mass cause a torque about the handle, causing it to spin, but it may not be as simple as that.

i also like the tags for this question :)

marinelife's avatar

@harp waterskier 2007 makes a great point regarding your tags. Who knows what additional laws of physics Sir Isaac Newton apprehended after he threw the apple in reaction to the bonk on the head?

Personally, I call it home despair when I have to do it.

Harp's avatar

OK, here’s a bit more experimental data for you. I just balanced a hammer by adding weight to the claw side so that the hammer’s head balances at a point along the axis of the handle. And it still flips!

waterskier2007's avatar

im confused, which way did u balance it?

Harp's avatar

Well, before, the “face” side of the hammer was slightly heavier than the “claw” side. I determined this by resting the hammer head on the edge of a small strip of metal placed under the centerline of the hammer’s handle. It tips to the face side (this was the case for all my hammers). So i added weight to the claw until it no longer tipped.

eambos's avatar

That’s a very interesting conundrum. Now I’m intrigued.

waterskier2007's avatar

hmmm, im really confused and i wanna figure this out bad.

Knotmyday's avatar

This question is great! I believe it has something to do with the euphemistically termed “Law of Variables” or “Law of Variation, ” stating that the probability of a piece of buttered toast falling face down on the floor is proportional to the cost of the carpet.
Here is a hilarious experiment on the subject. Don’t click on the link to Thiel’s slightly more scientific version, ‘cause it’s DOA. Here is the good link.

waterskier2007's avatar

yeah but that has nothing to do with his question. if he were asking, why does it land with the claw side digging into my hardwood floors, it would make sense that you post as you did. but hes asking why it spins so that the sides end up opposite when you catch it

mvgolden's avatar

It has been a while since I have whipped out my dynamics, but I think it has to do with the angular moment of inertia. When you balanced the hammer you made the integral of the mass times the distance to the center line equal on both sides. [Integral(x*dm) or Sum(x*m)] But the angular rotation is control by the angular moment of inertia which is the integral of the mass times the distance to the center line squared. [Integral(x^2*dm) or Sum(x^2*m)]. I’m not sure if that is totally valid way to look at it.

A great experiment would be to get a sledge hammer or rubber mallet and see if they do the same thing. Just watch the toes and the floor.

boffin's avatar

Are you above or below the Equator…
Like water in toilets…..

Harp's avatar

OK, so I tried this hammer, which is, as far as I can tell, symmetrical. It flips.

Lest you be saying to yourselves “this moron is putting some slight spin on the hammer without realizing it, then milking it for all the fluther mileage he can get”, I can hold the hammer so that the face points directly up (or down) and throw it all day long without flipping it.

I hope some of you are confirming this stuff at home.

mvgolden's avatar

@harp I believe that you are trying not to put spin on it but are you sure that just the nature of the more or less oval shaped cross section of the handle and the shape of your hand doesn’t put a spin on it? I don’t have a appropriate hammer at home. I can try with one at work tomorrow.

What about taking a circular dowel with a weight on the end and trying with that? Or you can build one out of pvc pipe and sand.

I tried it with the two claw hammers I have and both twist. Wild!

Poser's avatar

I suspect mygolden’s first answer is closest to the solution. I have tried similar experiments, and achieved similar results with other objects, most recently with a pack of Orbit gum. For those who are interested in repeating my results, I’m using the new Positively Pomegranate flavor with two pieces gone from the pack. That’s just what I had sitting on my desk when I read this question.

I find that it is quite difficult—though possible—to toss the pack of gum flat without it twisting. In other words, if I hold the pack in my hand so the large flat sections are facing up and down, and flip it one or more times, it almost always twists. If I hold it so the flat sections are facing left and right, I can spin it many times without it twisting. In other words, if the axis or rotation is perpendicular to the plane of the large flat sides of the pack, no twisting. If the axis of rotation is parallel, it twists.

I suspect the same properties of physics that are causing your hammer to twist one way and not the other are also causing my gum to twist. I just don’t know what properties those are.

And it just occured to me that perhaps Orbit gum wasn’t the best choice for this experiment. I’m going to go find some Trident.

Harp's avatar

Poser, I’m not going to call into question the validity of your research here, but I would just like to say that I find that the use of gum as an experimental subject robs the whole project of its edgy, testosterone-fueled recklessness. The actual science of this is only a small part of it; we must also respect the overall aesthetic imparted by the use of dangerous materials. Now if you were to use a real trident, I would be totally down with that.

By the way, although it’s a minor violation of the above stated principle, I tried this with a rubber mallet. It flips too.

Poser's avatar

Good point. I’ll go get my shotgun.

Harp's avatar

Yesssss!

waterskier2007's avatar

try it with a human baby

Harp's avatar

I did. Too wiggly.

eambos's avatar

Small dogs don’t enjoy it either, but I did have the same results.

marinelife's avatar

@harp That cracks me up. This thread just took an amusing turn.

Harp's avatar

Um, Marina, If you don’t have a serious empirical contribution to make here, could you please just stand out of the way so you don’t get hurt? Thanks.

eambos's avatar

I would still like to know the real reason for the flipping. Are we in agreement that mygolden has found the answer?

Harp's avatar

Well jeez, if we must be serious…

I’m actually starting to convince myself that the answer lies in the subtleties of the throwing motion. Here’s why: If I throw with my right hand, the head flips in a CW direction (from my perspective), but if I throw with my left hand it flips CCW (although it’s awfully hard to both watch the head and catch the handle with that hand). If the flipping is due to factors proper to the hammer itself, I would expect the same direction from either hand. What do you all think?

Poser's avatar

Does the direction change depending on which way the head/claw was oriented? IOW, head left/claw right or head right/claw left.

Harp's avatar

Nope, appears to flip the same direction either way. But I would love to have someone else confirm that (and yes, with an actual hammer).

Harp's avatar

Maybe the reason it doesn’t flip when the longitudinal axis of the head lies in the plane of rotation of the handle is that the head then has a gyroscopic effect that resists the flip?

Poser's avatar

Hold on. I’m trying to find my hammer.

waterskier2007's avatar

it has to be the subtleties in the throw, if the data that Harp is stating is correct. im at work right now but on my break i will grab a hammer and test it out

Harp's avatar

Never before has so much human energy been expended for so little

Poser's avatar

Alright. Found my hammer. Lest the manliness of my research be called into question again, I performed my tests barefoot in my garage while standing in between a lawn mower and a very fast sportbike. I achieved the exact same results. I even tried imparting spin on the hammer to see if I could counteract the twist I was getting, to no avail.

I think Harp’s gyroscopic theory has merit, but that fails to explain the twisting when the longitudinal axis of the clawhead is perpendicular to the plane of rotation.

After having performed this experiment with an actual hammer, I don’t know if my pack of gum research is quite valid, or at least comparable. I think the weight of the hammerhead has too much of an effect on the center of gravity of the hammer to compare it with a pack of gum. What was I thinking?

How about the relative aerodynamics of the claw and the head? Perhaps the curve of the claw imparts unequal lift to that side of the equation.

mvgolden's avatar

Couple things. First, My screen name is mVgolden. I am not sure why lots of people see it at mYgolden.

Second, I tried it at work today with a ball peen hammer. Still spins. Bitchin’! Did not see a mallet. If I have time I will look tomorrow.

Third, just tried it with a screw driver and it still spins even though it is total symmetrical about the long axis. While the screw driver is not a many as a hammer it is a very large screw driver which helps some. I also put black and white duct tape on the handle to help me tell if it spun. I think colored duct tape makes up the manliness lost using a screw driver rather than a hammer.

Knotmyday's avatar

A real man would have used a lit road flare. Or a stick of dynamite. And he would have chewed the markings on rather than using tape.

eambos's avatar

I used a knife, and my own blood to mark the sides.

Harp's avatar

Good work gentlemen. Here’s a video of my latest trials using found objects and a variety of throwing methods. I’m hoping that the slow motion will allow us to better analyze what’s happening.

eambos's avatar

2001: A Space Odyssey?

Harp's avatar

Yeah, I’m not thrilled with the title either, but It seemed better than “2008: The Great Flip-off”
Anyway, it’s the content that matters.

eambos's avatar

You’re leading me on, aren’t you? You can’t be that hairy.

Harp's avatar

I’m holding the camera. That’s my mom.

marinelife's avatar

I just love this thread. The reek of testosterone, the talk of tools. It’s getting me hot.

@Harp Is Thus Spake Zarathustra your theme song for this thread.

Harp's avatar

wow, this must be the mods’ night off

Back awaaaay from the hammer, Marina!

Response moderated (Spam)

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