There is no grape stagnation

by on October 27, 2016 at 12:23 am in Games, Sports | Permalink

Setting the world record for using your mouth to catch a grape dropped from the greatest height: It was a dream years in the making, and all it took was a hot air balloon, walnut-sized fruits shipped specially from Georgia and a crew of Ph.D.-level engineers who gathered at a tiny Vermont airport before the sun rose on Monday morning.

The man with the plan was Brent Fraser, 35, who said he “just had a natural knack” for catching things in his mouth ever since his high school days in Barre, Vt., where buddies would chuck food toward him in the school parking lot.

The piece has some good sentences, such as:

Indeed, once things did get going, most of the few dozen attempts ended with a goggle-clad Fraser getting smacked in the face and chest by the large grapes — selected because they were easiest to see — that were traveling about 56 mph.

And:

“How much did they hurt?” one of the engineers, Tristan Ramey, asked at one point.

“So bad,” Fraser told her. “I felt like I was being punched in the face.”

He ended up catching one from 101 feet.  And finally:

Fraser, most of his face stained in purple grape juice, had to get to work to interview a prospective employee by 9 a.m.

Here is the full article, with video, via the excellent Mark Thorson.

1 Ray Lopez October 27, 2016 at 12:55 am

Mark Thorson is a font of information! Doesn’t sound like a grape moving at 50+ mph would hurt that much, even one of those giant seedless globe grapes.

2 gab October 27, 2016 at 12:40 pm

Well, Mr. Fraser said it felt like “he was being punched in the face” so I assume it hurt pretty badly.

3 londenio October 27, 2016 at 1:50 am

Can 56 mph be the terminal velocity of a small sphere with the density of water? How big are these grapes?

In any case, I hope that job interview went well?

— Tell me something interesting about you?

— Well, just this morning, …

4 carlolspln October 27, 2016 at 1:55 am

Terminal velocity of a human is ~ 120 mph [extremities splayed]

A grape? 200-300 mph, easy.

5 londenio October 27, 2016 at 2:10 am

A 200-pound grape perhaps.

6 londenio October 27, 2016 at 2:15 am

I looked it up. There are tables for hail, which have a similar density to a grape. But you for a sphere you can compute an approximate terminal velocity. And it seems that a sphere of diameter 3cm (a big grape) would fall at about 55 mph.

http://hyperphysics.phy-astr.gsu.edu/hbase/airfri2.html#c5

I still would like to see an actual measurement. Does someone in this comment section live in a high-rise and has a big grape and a stopwatch at hand?

7 londenio October 27, 2016 at 2:20 am

Sorry, last comment.

I still think the number is a huge overestimate. For something as small as a grape, going through air, the traditional equations assuming quadratic drag should not apply.

Anecdotal evidence: I have been hit by grape-sized hail on my head. It hurts. But that was not a 60mph impact. We are getting into bullet territory at those speeds.

I think I used up all my commenting rights for today.

8 a Fred October 27, 2016 at 2:44 am

Slowish bullets go about ten times that speed, ie 600mph.

9 Troll me October 27, 2016 at 9:25 am

Bullet speeds are usually measured in ft/s, and that would be a slow bullet.

10 Troll me October 27, 2016 at 9:24 am

Water is denser than ice, ergo grapes are denser than ice, ergo they have less surface area to cause friction and hence slowdown than hail, ergo terminal velocity of a grape should be somewhat higher than hail (the percentage reduction from an infinitely dense object should be roughly proportional to the square of the proportional difference between its density and that of hail).

11 a Fred October 27, 2016 at 6:21 pm

“Bullet speeds are usually measured in ft/s, and that would be a slow bullet”

Yes Nathan, hence the first word in the sentence you responded to.

Re choice of units: when entering an ongoing discussion, expressing quantities in the terms already in use might be seen as more polite than trying to score pedantic points. If maximum pedantry is required, then bullet speeds are “usually” measured in m/s.

12 Thiago Ribeiro October 27, 2016 at 4:23 am

Another victory of the human spirit.

13 Thiago Ribeiro October 27, 2016 at 4:30 am

“Fraser, most of his face stained in purple grape juice, had to get to work to interview a prospective employee by 9 a.m.”
Touched by Mr. Fraser’s example, the prospective employee decided to persue new challenges in another place.

14 Seth Green October 27, 2016 at 8:15 am

surely you mean there is no *grape stagnation,* eh? eh?

15 Ray Lopez October 27, 2016 at 8:53 am

…or for Trump supporters, no *grate stagnation*, da dah dumb…

16 terminalillocity October 27, 2016 at 12:23 pm

You guys arguing about terminal velocity, etc. don’t seem to realize that the height the grape was dropped from wasn’t high enough for terminal velocity to have been reached at the time of impact.
Dropped at a height of 101ft, without any air resistance, the time of impact is 2.5s. Since g = 32ft/s, this means its velocity upon impact is 80ft/s, which is approximately 55mph, the number in the article.
To reach terminal velocity, the grape would have to be dropped from a greater height.

17 carlolspln October 27, 2016 at 3:47 pm

We know that.

The thought experiment was ‘terminal velocity’.

18 a Fred October 27, 2016 at 6:38 pm

I liked the nice match between observed and calculated v. The team took an HoM (height of mouth) measurement. Is this required by the sanctioning body?

But who noticed the wood-pile dinosaur?

19 Brent Fraser October 30, 2016 at 7:51 pm

You nailed it Terminalillocity. We calculated that in order for a grape of the size we used, a grape would have had to have been dropped at approximately 200 feet to reach terminal velocity. The grape was dropped from 101 feet and had a speed of 56mph. In case people were wondering, the terminal velocity of those grapes were approximately 78mph.

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