So, I am a teacher and am starting a physics problem of the week, but cant think of a great deal myself, so I thought why not start a thread on here and the brilliantly intelligent and generous patrons of this fine establishment might get stuck in Ill start though - rules are the same as for any thread of this nature, first person to answer puts up the next problem (or if you have a problem but no answer you can try and give it to the person who wins via pm or via nomiation in the thread).
Do the: "if a plane starts take-off from a conveyor belt that matches its speed rolling in the opposite direction, can it still take off?" problem. Then ask how a wing generates lift. Then ask why planes can still fly upside down. By the way, 66.66 metres.
I think that's incorrect, as the troupe wasn't standing still! You can't just divide the distance traveled by the officer 3 times.
Ummm. Am I right in thinking that can't actually be answered since you need to know the speed of either the General or the troupe to work out the rest? EDIT: And no, please don't do the: "if a plane starts take-off from a conveyor belt that matches its speed rolling in the opposite direction, can it still take off?" problem because it wont, not until there is a prop driven aircraft which can push enough air over the wings itself to generate the required lift to raise the aircraft. That Mythbusters episode was complete BS since the plane was quite clearly doing about 30-35MPH when it took off, even the model was moving forwards.
We used to create a function/equation for problems like this, so you could basically plot a graph displaying a range of distances traveled by the troupe vs a range of speed factors for the general, or you could just input 3 as the speed factor for the general and solve for the desired distance... but fcuked if I can remember how to do that crap now
You got in before i finished my post edit lol. No, that episode was complete and total BS. Every single version of the test they did was BS since in every single one the planes were moving long before take-off, even the models. It actually made me stop watching mythbusters for a while.
Dude, we're not talking about a fast car (which puts load against the ground to move forward) with wings attached! In which case a conveyor belt runway moving at the same speed, would mean the car stays perfectly still. We're talking about a plane which is moving due to force on the air, not the ground! So with the conveyor belt running at the same speed, the wheels just have to spin twice as fast, so it's just a bit more load due to friction in the wheel bearings, but that's nothing compared to the weight of the plane, so it still takes off! please for the love of Jesus, Mary and Joseph tell me you agree
Heh, someone beat me to it . That was exactly what I understood the problem to boil down to... The aircraft can still move forward because it's forward thrust/momentum is not being generated by the wheels, it's being generated by the propeller. Which will pull it forward no matter what surface it's on. Even if you could get the conveyor speed to match the speed of the aircraft's forward movement, it would just make the wheels spin faster - as mvagusta mentioned, it only has to overcome the friction/load of the wheels. Mythbusters don't always get it right though, I'll grant you that. In fact some of the stuff they have done has even been contradicted by Top Gear! Such as a moving vehicle behind the blast of a jet engine (in the first series, Mythbusters did not make the car flip - TG did it years before), and beating a speed camera (although that was only possible because you need two photographs in this country).
Common misconception. The plane still moves forward even though the convener belt is moving backwards. For example, if the plane is moving forwards at 5mph the belt is moving backwards at 5mph so the wheels are spinning at 10mph. Assuming no friction this has no effect on the plane. With friction considered on a fully loaded cargo plane, one might argue that either the bearings or the engines would overheat before lift off. Nexxo has executed a successful troll.
Well, it's not really a troll in an educational context as it gets people talking about the phyics of it. Regardless of what you think would/should happen, it's still interesting to discuss. But yeah, Nexxo may indeed just be trolling!
I still don't get how people can't understand the whole plane taking off thing. It must be some folks' brains are just wired wrong, because it seems to fundamentally simple to me. I've got a few good ones memorised, but they're all special relativity ones (they made the best impression on me while I was learning it), so a bit much for asking kids.
Ah man, tea spilled everywhere in laughter moment after reading that. I take it you are being sarcastic...
Yes you can. Because the officer is moving to the front of the troupe, and then to the back again, in the opposite direction that the troupe is moving. The extra distance travelled by the officer to get to the front of the moving troupe is cancelled out by the comparatively shorter return trip to the back of the troupe coming up to meet him.
That's correct actually... I haven't had enough dairy today The 100m is not a stationary marker, it's the length of the moving troupe
Lets move on If you have a bird flying in a train, will it hit the back of the train when the train goes? Or some variant of that, you can embellish as you please. A good on is if you have a balloon floating with neutral bouyancy in a car, and you accelerate what direction does the balloon move / what does it hit first in the car? What part of a train is always moving at twice the linear speed, what part is always stationary whatever the speed, and what part is always moving *backwards* no matter how fast the train is moving forwards? Lets see you answer those b!tches
Wheel top/bottom/centre, but then you can delve into the sticky mess of angular velocity. As for the balloon and bird, both will move if the vehicles accelerate, as they are not fixed by anything inside. The bird will be more complex than the balloon, but they will both be accelerating in the vehicle's reference frame.
