Japanese balls play by the rules

Wicked backspin from the ball launcher.

1. The machine is made to pitch fastballs, which have topspin. On hitting the ground with no forward velocity, the spin would make the ball take off forward on contact with the ground.

2. At 10 km/hr, we may have seen a different result. At 100 km/hr, the vehicle drag is substantial, and we have no model of the airflow around the truck. The ball may have 'drafted' the truck, to use the racing term, getting 'sucked along' behind it.

3. We have only an assertion that the two speeds were matched, but I saw no evidence that the speedometer was calibrated (or that the needle exactly met the mark) or that the speed gun was calibrated, or that there was any way of checking how closely matched the speeds were. Any mismatch would result in a nonzero lateral velocity.

I think it worked remarkably well for the crude setup.

But the real curiosity is, why did the driver wear a helmet and protective jumpsuit, while the poor guy on the flatbed had neither? Wouldn't the guy in the back be in far more danger in case of accident than the guy inside the cabin, with (presumably) seatbelt and airbag?

I love how the driver, seated comfortably inside the cab of truck moving only about 60mph, is wearing a crash helmet, while the second guy, exposed in the back of the truck and operating a machine with unshielded parts rotating at high speed, doesn't.

I love the way they build the suspense up. Now that is gripping science! Sugoi!

Roy:
"1. The machine is made to pitch fastballs, which have topspin. On hitting the ground with no forward velocity, the spin would make the ball take off forward on contact with the ground.

2. At 10 km/hr, we may have seen a different result. At 100 km/hr, the vehicle drag is substantial, and we have no model of the airflow around the truck. The ball may have 'drafted' the truck, to use the racing term, getting 'sucked along' behind it.

3. We have only an assertion that the two speeds were matched, but I saw no evidence that the speedometer was calibrated (or that the needle exactly met the mark) or that the speed gun was calibrated, or that there was any way of checking how closely matched the speeds were. Any mismatch would result in a nonzero lateral velocity."

I'm discounting #2 and #3. The slow-motion shots at the very end make it clear that the ball falls straight down after release, from the point of view of the stationary camera, or at least close enough to it to require instruments to tell the difference. If the draft from the truck were impacting the flight significantly, you'd see it during the beginning of the fall, and if the ball had a forward vector on release, you'd see that in the slow-motion video as well. Neither of those is the case--it drops straight down, then starts chasing the truck on the bounce. I'm going to go with #1, other than to correct the terminology: curve balls have topspin, fastballs have backspin. Clearly, this ball had some backspin, as the bounce took it opposite to the direction of launch.

What I saw is exactly the same as when I just drop a ball with a hard top/bottom spin on it. What we saw might well have been just a drop with spin.

I've seen clips from this show before, but what really entertains me about these stunts is they stole the theme from that Keanu Reeves / Sandra Bullock movie Speed.

I think it's a combination of 1 and 2 plus the air resistance. On the slow-motion, you clearly see the ball going a bit backwards before touching the ground.

The air resistance would slow down the ball. Added to the drafting effect, that would be enough for the ball to have a forward movement.

You can see it on the slow-motion, that ball has a very small forward component just before touching the ground.

Then, as soon as it touches the ground, the spin would get the ball moving a lot more.

Now a question, how much top spin would be needed to counter the air resistance + the drafting effect !!! Or another one, what speed you need to give the ball to have it touch the ground at the point it ejects the launcher.

To be sure you can repeat time after time, you need a cruise control in the truck, not the foot of a driver. You can calibrate the truck/cruise-control device with the same radar you use to setup the throwing device.

Cheers,

Richard

Actually, when you think about the way the machine shoots the balls, it does not put spin on the ball. Both of those wheels turn at the same rate. They were not using it like they would a football. Both the wheels were upright, parallel to each other.

Those machines are perfectly capable of putting spin on the ball. In fact, they are designed to do so, so that coaches can train their team on various pitches (baseball) or various spins (tennis). They would be useless without that capacity.

It is probably a combination of air resistance and the wake effect of the truck, as was mentioned above. The non-spinning ball would not penetrate the resistance as well as a spinning ball.

In baseball, fastballs are spinning while pitchers try to eliminate spin with the knuckleball, which makes its trajectory more difficult to anticipate even though the ball is going slower.