Good video. But...

"The speed of an assault weapon is substantially higher than the speed of a handgun".

No. The velocity of the projectile from a centerfire rifle is generally much higher than that of a centerfire pistol. It does not matter if the rifle is semi-automatic or not. The velocity of the projectile from a rimfire rifle is also generally much higher than that of a centerfire pistol. But rimfire rifles have very low projectile weights and deliver substantially less energy, have substantially less momentum, have generally smaller projectile diameters, and hence are much less lethal than centerfire pistols.

Some projectiles are designed to tumble. Most projectiles for disrupting flesh are designed to flatten out (and not fragment).

Haven't viewed the video yet, but just common sense tells me no propulsion system is 100% efficient, so the losses over time will be larger, and less efficient in overall fuel use.

It's like the most efficient way to drive a hybrid is to floor the accelerator to get to speed, then try to go as fast as possible, using as little accelerator pedal as possible.

Conversely, the rocket would just be wasting fuel trying to slow down before it had to full burn to stop in time.

I'm just impressed they keep the terminal velocity down enough they don't need to use drogue chute(s).

Uh, what? Nobody said that at all. It is neither a "classic example" nor an assumption. The trajectory has been tracked since it was discovered, which is hyperbolic around the sun, and the speed of the object is such that there is no way it could have accelerated to its current velocity due to the gravity of our sun alone, hence it has to be interstellar, picking up kinetic energy from another system outside of our own. The orbit is not improbable, it is unusual compared to trajectories of asteroids that exist within our own solar system. Sharpen your crayon there bud, and stop trying to impress people with your new thesaurus for hipsters (come on, "undergird"?? Really?)

This must be the civilian version. I am convinced that, like the hoola hoop, the original metal Slinky was actually a failed experiment by the defense industry to create a hand thrown weapon that could inflict great entanglement on the target, and with sufficient velocity, bleeding. At least that's how things normally wound up when we got bored of walking them down the stairs and started swinging them over our heads.

Needs a fan with motor speed keyed to the apparent slide velocity blowing at her

10m with a rifle seems too easy. Even with a crappy air rifle (BB gun, really, so not even actually rifled and probably much lower velocity), I can put every shot in a one inch circle from that far away. They are shooting pretty small targets though, and you can make a competition out of mm differences so I guess it works.

I've never watched the shooting part of the olympics, but pistols seems cooler.

I wonder if there are groups who do this sort of thing around me. I like shooting, but since I live in the city, I don't really want to own a real gun. An airgun might be an interesting alternative.

What if you ran it backwards? Velocity is directional... No?

I guess the hint for these is the rotational test that they show at the first.

1) A sticky object that would let go like a wall crawler that climbs down a wall would create this effect. (see below)
2) You can't. As you approach infinite speed it would get very close. (see below)
3) The bike will move forward. (see below)
4) The outside parts of the wheels that overlap the rail. Also if the train has a flywheel that is larger than the wheel size the bottom of the flywheel would also always move backwards faster than the train was moving.

1) He says "what object is inside?" so I'm not sure a liquid would count. Also a viscous liquid would flow a slow rate and would probably not stop and start. You might be able to get a viscous liquid to stop and start if you had fins, but that still might just move slowly or gain enough momentum to roll fast without any flow.

2) A little excel calculation shows that the average velocity approaches twice the initial but will never hit it.

attempted m/s - total time - average m/s
1 100 1
2 50 1.333333333
3 33.33333333 1.5
...
200 0.5 1.990049751
201 0.497512438 1.99009901

3) I'm not sure if the parameters of this experiment are explained sufficiently.

If it is allowed to slip then no matter the mechanical advantage a hard pull should always be able to get the bike to skid back and defeat friction.

If the bike is not allowed to slip on the ground then I don't understand how it could ever move backwards, the only options would be that it doesn't move at all or it moves forward.

If it can't slip then the ratio of the pedal to the wheel is what is in question. Bikes only have gear ratios higher than 1 and the crank is smaller than the tire so the tire will always rotate more than the crank thus the bike should move forward.

The track question seems really straightforward, so I must be missing something.

The question is how fast do you have to run the 2nd lap such that the average of the two laps (Vavg) is twice the velocity of the 1st lap (2V1); so Vavg = 2V1 (says right in the video). Unless I'm missing something, V2 has to equal 3V1:

Since the problem states that Vavg must be 2V1, we can substitute that in the average calculation below:

So, Vavg = (V1+V2)/2 becomes 2V1 = (V1+V2)/2

Now solve for V2:

V2 = 4V1-V1
of
V2 = 3V1

i.e. your 2nd lap must always be 3x faster than your 1st lap so that the average of the two laps is twice the velocity of the 1st lap.

No?

Are you sure about that? Let's say the track is 100m for simplicity's sake and you run it at 1m/s (so 100s).
If you ran the second loop 3 times faster, you run it at 3m/s and it would take 33.3s.
So, total time and distance is 200m in 133.3s at an average speed of 1.5m/s.

I think it's impossible.

Even if you ran the second loop 100000 times faster, your total time would be 100.001s and average speed would be 1.99998m/s.

It would only ever approach 2V1.

Unless there's something about rotational velocity (as opposed to speed) that I'm missing. Quite possible, given it's been a long time since I did any physics.

The purpose of the device (a gun) is to propel a projectile at great velocity. The purpose of the projectile is to sometimes kill or injure but mainly just put holes in paper. Just sayin'.

These days firearms are mainly used for shooting steel, cardboard and paper targets. I own competition guns made solely for shooting cardboard and steel. The market determines what they are built and bought for, not you.

Now, you've changed the topic to "responsibility". I hadn't seen anyone here argue he lacked responsibility for the operation of the device. On top of that, if the device is faulty and it malfunctions you are not necessarily liable for what happens. There is case law on this in the USA.

There are accidental shootings. I've literally got a degree in treating people who have been victims of accidental or purposeful shootings. There is lots of case law covering accidental shootings (and the law says that there are accidental shootings). Accidental doesn't mean there won't be repercussions.

Tesla enthusiast here. The Tesla vehicle is able to use its front-mounted radar to track one car beyond the car in front of it. How does it do this? It bounces the radar signal off the street underneath the first car. In this case the Tesla could determine the position and velocity of two vehicles in front of it and it predicted a collision, sounded the alarm, and applied the brakes.

So no, it's not that the cameras are tracking objects through another vehicle's windows (at least not yet). Radar can also see though zero-visibility conditions like snow and fog.

well, went to a mcdonalds today with my oldest kid, there was a couple of obnoxious bigger kids there sucking a little coke up into their straws and spitting it out high velocity around them, laughing.

we don't know the backstory so I think GOOD for him. nothing to see here, move along.

Eh, I'm not sure about that. Actual airflow is the same as whatever the small fan can move. The Venturi effect would just make the higher velocity airflow through the small fan channel into a lower velocity flow through the larger (main part) channel (it's basically a complicated diffusor). The actual rate of flow is the same. You probably actually lose a fair amount of efficiency because of all the ducting and diversion. I would also guess that small, high-speed fans aren't as efficient as larger low speed fans for the same airflow.

That isn't to say it isn't a cool design, though. But yeah, for just getting the job done, a box fan is probably more efficient and effective.