OT--Physics Question

Jiles

Well-known Member
Many years ago, I was given a written test during a job application.
There was a series of test, but one stuck with me.
The situation was ---
A picture of three cannons.
One cannon barrel was straight up.
The second barrel was at a 45 degree angle.
And the third barrel was horizontal.

The question was [i:ed68e4b745]"which cannon ball will [b:ed68e4b745]travel[/b:ed68e4b745] the farthest?"[/i:ed68e4b745]
I answered cannon shooting at 45 degrees.
My answer was wrong! I never found out why!
Oh I got the job anyway and worked there for 31 years!
 
Traveling (in this case) means maximum distance traveled. not farthest from the muzzle. Shooting straight up keeps the projectile in the air longest and traveling the most distance (though not horizontal distance. Jim
 
(quoted from post at 03:50:56 11/23/14) Traveling (in this case) means maximum distance traveled. not farthest from the muzzle. Shooting straight up keeps the projectile in the air longest and traveling the most distance (though not horizontal distance. Jim

I agree but, there can be certain conditions that would effect the outcome.
What if this test was done in the desert? Cannon shooting horizontal would travel the shortest.
If test was done on a frozen lake, Horizontal would probably travel the greatest.
I never knew the answer they wanted and several others answered same as me?
I don't have three cannons to do the test LOL
 
Correct. Straight up and same distance back down is further than 45 or horizontal. It is not a physics question as much as a "reasoning" question.
 
An assumption was probably made that it was till touchdown. if so a cannon fired horizontally from the International Space Station in a Forward direction might go into orbit around the Sun. If fired from 6 inches above grade horizontally, it might go a hundred yards. Assumptions are clearly needed. Jim
 
Best as I can recall from Physics 101 the 45 degree angle is correct as far as distance from the point of origin to farthest landing spot.
 
They ask for the farthest distance. lets say that one shooting straight up goes 5000 feet. Then it comes back down another 5000 feet. They didn't ask which one was going to shoot the farthest from the cannon at ball impact.

Rick
 
I wonder how much difference there actually is since the one fired at 90° has to stop and reverse directions while the one fire at 45° continues on in the same direction until it hits.
 
(quoted from post at 05:06:51 11/23/14) I wonder how much difference there actually is since the one fired at 90° has to stop and reverse directions while the one fire at 45° continues on in the same direction until it hits.
And when it hits, how far will it roll?
 
(quoted from post at 21:06:51 11/22/14) I wonder how much difference there actually is since the one fired at 90° has to stop and reverse directions while the one fire at 45° continues on in the same direction until it hits.

Good question. Thing is the round is going to travel until it runs out of energy. Then gravity does the rest. The initial energy isn't spent turning it around.

Rick
 
I'm assuming the question contemplated the one-way
travel of a projectile, not the there-and-back
thing. I don't know beans about physics, but it
seems to me that a projectile fired straight up
will maximize the energy supplied by the charge.
Gravity will deflect a projectile fired at 90
degrees or horizontal into the earth before the
energy of the charge is maximized.
 
Taken from: Khan Accademy
Air resistance is the answer. Basically, at 45 degrees you are spending the most TIME in the air, which would mean the most time to be affected by air resistance. As you reduce the angle, you lose a little time in the air, but gain distance as this also means less air resistance. The air resistance factor is more significant than the extra distance gained at the ends of a 45 degree arc. Jim
Higher math
 
(quoted from post at 21:35:48 11/22/14) I'm assuming the question contemplated the one-way
travel of a projectile, not the there-and-back
thing. I don't know beans about physics, but it
seems to me that a projectile fired straight up
will maximize the energy supplied by the charge.
Gravity will deflect a projectile fired at 90
degrees or horizontal into the earth before the
energy of the charge is maximized.

And that's why the OP got the question wrong I think. They ask which one was going to travel furthest. They didn't specify one way. I think it was more of a logic question than physics.

Rick
 
Actually, I think "straight up" is the correct
answer either way---there-and-back or one-way.
 
Either you're not describing the question correctly, or their "correct" answer was wrong. Assuming "distance travelled" means the HORIZONTAL distance, then 45 degrees is correct.

But what if they meant actual distance of the projectile's trajectory? Assuming the cannonball stops when it hits the ground, zero degrees is wrong, leaving 45 and 90. If we ignore the effect of air resistance, the projectile's VERTICAL travel will be the same for both 45 and 90 degrees. That's because it goes up until its kinetic energy has been converted to potential energy, and potential energy is a function of elevation. If the cannonball goes straight up and straight down, that's a shorter "distance travelled" than a parabola of the same height. Factoring in air resistance is going to change that a bit, but since we don't have enough information to calculate air resistance we have to assume it doesn't significantly affect the outcome. So the answer is still 45 degrees.
 
Being the smart arse that I am I would have said "none" cause no one brought a match to light any of the cannons. It does not say that the cannons were lit.
 
Did my time as an instructor at artillery school (Ft Sill Okl) That question was thrown at many a potential "cannon cockers". The answer is "straight up".

Did a fire power demonstration @ Sill in 1977. We took 2 M109's, (SP 155's) pointed one almost directly at a target about 2 miles out. Had 2nd tube aimed ALMOST vertical. Fired #2, waited what seemed like an eternity, and fired #1. Both shells impacted at exact same time. Has little to do with the OP's question, but was pretty cool to see!
 
Gotta read the question and not something into it. So I have to go
with old tanker on this. It's going to do all the stuff Mark B pointed
out but the question is about distance the ball traveled and the way
I see it straight up is the longest path.

However my knee jerk reaction was to answer the question as which
will GO the farthest and I picked 45 and lost.

Mark
 
The closet way to get from one point to another is a straight line which would be the horizontal shot
the 45 degree shot would require the cannonball to travel up as well as out.Or look at it as 90 degree triangle the line opposite the right angle has to be longer to get to the same point.
 
I realize I made a mistake in my earlier analysis. The projectile fired at 45 degrees won't go as high as the one shot vertical, because its velocity has both horizontal and vertical components. Only half of its kinetic energy is vertical, so it only goes half as high as the one shot vertical. If we approximate the parabolic path of the projectile as a circular arc, the distance traveled by the 45 degree projectile is pi x 1/2 x h, where h is the apogee of the vertical projectile. So the total distance travelled by the 45 degree projectile is about 1.6 times the maximum elevation of the vertical projectile. But the vertical projectile travels twice its maximum elevation so it beats the 45 degree projectile by about 25 percent.
 
The concern about the exact wording of the question is a real concern. However if the question is as described then the stated answer is wrong--45 degrees is correct.
It's all about getting the maximum range. Straight up travels 0 distance or however much the wind blows it off course. horizontal and 45 degrees brings in a discussion of gravity. Gravity is a constant Force which is acting all the time and as soon as the round leaves the barrel begins to pull it to earth. When it reaches the earth forward travel is over, in this question. To counteract the pull of gravity 45 degrees maximizes the forward travel.
BTW that is also the way every physics textbook will answer the question--45 degrees.
 
artillery fire from various points can be timed to impact at same location at exact same time. That's done with a method referred to as "time on target". It's done by careful calculation of elevation of the gun tube. Rounds fired at flatter angle reach target sooner that a round fired higher. Distance from firing point to impact is controlled by charge behind shell. A round fired at high angle of departure, provided it has ample charge behind it, will travel FARTHER than one fired at a flatter angle by virtue of the fact it will travel to fullest extent charge will propel it, then return an equal distance to earth.

Lot of variables left unmentioned....Size/weight of round. Size of propellant charge, and even to a point, design/type of gun tube. Provided all calculations are done correctly, highest angle of fire will travel greatest distance, but not always greatest distance FROM firing point.

Take it from an old artilleryman.
 
One of those "thinking outside the box" questions that someone from HR threw in to make himself feel important.

The proper answer is: "The question is ambiguous".
 
"which cannon ball will travel the farthest?"
If farthest means range, your answer is correct, 45
degrees.
If farthest means greatest height, then straight up
is correct.
If cannon is on a very high cliff, then horizontal
is correct.
 
It's not as much a physics question as a reading
extrapolation question. The answer would be
straight up. All 3 balls will go out varying
distances. but only one is coming back at you.
Thus it effectively doubles it's distance of
travel.
Dave
 
Was the job at a mutions factory?
Or was it at biscuit factory to see how many biscuits you could stuff in a can?
 
The test was a lengthy standardized one. I don't remember if any one actually finished or not.
We were given something like 15 minutes and I remember passing on a few questions. I didn't spend a lot of time on this particular question and just marked 45%.
I think it, along with a few other questions, was given to absorb time.
I also remember a picture of about 15 gears of different sizes, driving each other. One gear had an arrow indicating direction and the question was, "what is the rotational direction of gear ?"
That was not a multiple choice question but a time consuming one.
I think one reason I remember this particular question was that after the test, there was a lot of discussion, among ourselves, pertaining to this question.
Just wish I could remember more.
 
(quoted from post at 16:10:12 11/23/14) Was the job at a mutions factory?
Or was it at biscuit factory to see how many biscuits you could stuff in a can?

Machinist application at a large manufacturing plant.
 
I don't go in to see my physic nearly enough, so she says. I think that she's just trying to drum up business at my expense. But, she does say that that I do need to schedule physics more often, and when I step on the scale, she says that I should get more physic exercise.

Congratulations on the new job. Did they require you to take a physic first? Mine did, and I got the job too, so I must not be in as bad physic shape as my personal physic says.

Good luck, and with Thanksgiving being a few days away, start the extra turkey drumsticks soaking in bourbon today. I prefer Jack Black Old No. 7, myself. Don't wait until the last minute or the flavor won't soak in to the bone.

Mark
 
In my opinion this question has nothing to do with
range. The ball going straight up expends all
it's energy overcoming gravity, thus using all its
forward momentum gaining distance. Any other
angle still has forward momentum when it hits the
ground thus loosing distance.
 
BUT! That"s not what the question asked. It asked which would travel the furthest...TOTAL distance traveled is what it wants. Straight up in answer.
 
After rethinking the question, the curved distance traveled by the 45 degree angle may be correct. At 45 degrees the vertical height will be slightly more than 70% of the vertical shot and the range will be max. So, I'm going with the 45 angle because the curved distance is greater than just the vertical distance.
 
You are correct. If firing horizontal as in direct fire, you need to use a higher charge(white bag). At least that is what we used. (M114) So to me a cannon round fired in the horizontal position would not go as far as one fired at 45 degrees or the verticle position. I know what you are saying Just sticking my 2 cents in.
 
As others have mentioned, the correct answer is the cannon that fired straight up. People think that because the cannon ball lands 1 yard away from the cannon, it measured as a 1 yard shot. They totally forget about the 10,000 feet it went straight up and the 10,000 feet back to earth for a total of tiny smidge over 20,000 feet. The other shots make it farther away from the cannon but the total distance traveled by the cannon ball is less and that is the trick of the question.

I have had this conversation with a very socially awkward genius one time, he was drafted in the very early 1970s and being very smart realized that if he did well in artillery schooling, he could pick his placment. He was top of his class and picked the most dangerous assignment he could find... in California. Thats important because it ensured he could live to tell the tail of how smart he is, which he tried to not let too many days go by without doing....

Anyway, one time myself and another were talking ballistics for hunting/target rifles and Mr. Peabody gets drawn in just to tell us how to figure it out on paper using a slide rule. Cool but other than the challenge of figuring it out, he really didnt care (anti-gun pacifist). Eventually, the other guy I was talking to brought the question around to the very one being talked about, which of the 3 shots will travel the farthest. Well low and behold, Peabody not only knew the answer and how to figure it out but he had seen that group of questions at an interview as well as the other guy and started telling us all about it. Well Peabody was the type to tell you how to build a watch rather than tell you what time it is, even if I was just trying to be sociable when I engaged him, long story short, 4 beer later I had to get out of there and let him jabber away with the other guy.

To the point, the cannon fired straight up has the projectile that travels the farthest, even if it lands inches away from where it started. It also should be noted that the questions at the interview used to be quite common during the interview process although they seem to be a lot less popular now. Now, it think a persons personality at the interview is the most important thing. Go figure.

Just think, for 20 years I have been wishing I could have that hour and a half of my life back, only to find out it does have a small bit of relivance to real life... but to be fair, I did learn a little about .308 and steel silhouette shooting that day too so ya know, I got that going for me...
 
(quoted from post at 02:43:11 11/24/14) As others have mentioned, the correct answer is the cannon that fired straight up. People think that because the cannon ball lands 1 yard away from the cannon, it measured as a 1 yard shot. They totally forget about the 10,000 feet it went straight up and the 10,000 feet back to earth for a total of tiny smidge over 20,000 feet. The other shots make it farther away from the cannon but the total distance traveled by the cannon ball is less and that is the trick of the question.

I have had this conversation with a very socially awkward genius one time, he was drafted in the very early 1970s and being very smart realized that if he did well in artillery schooling, he could pick his placment. He was top of his class and picked the most dangerous assignment he could find... in California. Thats important because it ensured he could live to tell the tail of how smart he is, which he tried to not let too many days go by without doing....

Anyway, one time myself and another were talking ballistics for hunting/target rifles and Mr. Peabody gets drawn in just to tell us how to figure it out on paper using a slide rule. Cool but other than the challenge of figuring it out, he really didnt care (anti-gun pacifist). Eventually, the other guy I was talking to brought the question around to the very one being talked about, which of the 3 shots will travel the farthest. Well low and behold, Peabody not only knew the answer and how to figure it out but he had seen that group of questions at an interview as well as the other guy and started telling us all about it. Well Peabody was the type to tell you how to build a watch rather than tell you what time it is, even if I was just trying to be sociable when I engaged him, long story short, 4 beer later I had to get out of there and let him jabber away with the other guy.

To the point, the cannon fired straight up has the projectile that travels the farthest, even if it lands inches away from where it started. It also should be noted that the questions at the interview used to be quite common during the interview process although they seem to be a lot less popular now. Now, it think a persons personality at the interview is the most important thing. Go figure.

Just think, for 20 years I have been wishing I could have that hour and a half of my life back, only to find out it does have a small bit of relivance to real life... but to be fair, I did learn a little about .308 and steel silhouette shooting that day too so ya know, I got that going for me...
Thanks--very interesting!
 
This kind of crap is IMHO useless in figuring out how smart/good/useful an employee will be. It used to be a time when having the common sense to know 45 degree shot would send a projectile further downrange would be a good thing. Do you really want an employee that would try to shoot a cannon at a distant object without allowing for ballistic arc? Is it really good to have an employee that you have to explain what should be common assumptions to?

I think the best answer to any question like that is, "it depends". Perhaps following that with, "assuming your question means X then X but as that seems obvious I assume you are asking from a non-common point of view. Can you further explain the point of view from which you wish your question answered?"

Humans are not computers--we make assumptions. That's a good thing. You don't have to program us with every specific detail of your question, we can make logical assumptions. I also assume in interviews stupid questions are trick questions.
 
But what about the powder charge? A light charge and the horizontal ball might roll a good ways, while the verticle cannon might only go several feet in the air.

not enough information.

Gene
 
Useing your rules I'd hate to use a deer rifle you sighted in.Common sense would dictate that the question meant how far as in how far from the shooter would the bullet land.Actually a good question it'll weed out the technocrats and pinheads.
 
(quoted from post at 11:15:44 11/23/14) The test was a lengthy standardized one. I don't remember if any one actually finished or not.
We were given something like 15 minutes and I remember passing on a few questions. I didn't spend a lot of time on this particular question and just marked 45%.
I think it, along with a few other questions, was given to absorb time.
I also remember a picture of about 15 gears of different sizes, driving each other. One gear had an arrow indicating direction and the question was, "what is the rotational direction of gear ?"
That was not a multiple choice question but a time consuming one.
I think one reason I remember this particular question was that after the test, there was a lot of discussion, among ourselves, pertaining to this question.
Just wish I could remember more.

This question is pretty simple as long as all the gears have external teeth that are being meshed. Instead of figuring the rotation of each gear all you have to do is count the shafts on which they rotate in the proper sequence. All odd number gears will rotate one direction and all the even numbered gears will rotate in the other direction
 
(quoted from post at 19:02:56 11/24/14)
(quoted from post at 11:15:44 11/23/14) The test was a lengthy standardized one. I don't remember if any one actually finished or not.
We were given something like 15 minutes and I remember passing on a few questions. I didn't spend a lot of time on this particular question and just marked 45%.
I think it, along with a few other questions, was given to absorb time.
I also remember a picture of about 15 gears of different sizes, driving each other. One gear had an arrow indicating direction and the question was, "what is the rotational direction of gear ?"
That was not a multiple choice question but a time consuming one.
I think one reason I remember this particular question was that after the test, there was a lot of discussion, among ourselves, pertaining to this question.
Just wish I could remember more.

This question is pretty simple as long as all the gears have external teeth that are being meshed. Instead of figuring the rotation of each gear all you have to do is count the shafts on which they rotate in the proper sequence. All odd number gears will rotate one direction and all the even numbered gears will rotate in the other direction

The way I did it was to just take the pencil tip and go around and between each gear in the direction it will turn.
 
I understand the point everyone is trying to make about the ball being fired straight up, being the correct answer. However, from a logical point of view, I see nothing logical about firing a cannonball straight up in the air, unless the artillery men are suicidal!
 
(quoted from post at 07:44:50 11/24/14) Useing your rules I'd hate to use a deer rifle you sighted in.Common sense would dictate that the question meant how far as in how far from the shooter would the bullet land.Actually a good question it'll weed out the technocrats and pinheads.

The whole point of the question and the test itself is how a person answers it. Thats the way its designed. Its long so nobody finishes it, they [b:75bd77d1e9][i:75bd77d1e9]dont want[/i:75bd77d1e9][/b:75bd77d1e9] anybody to finish because then they can read into not only what questions a person answers but also what questions a person skips. The different questions bring out different types of thinking and highlights how a person thinks. This question is looking for a person that is detail oriented and does not read into things that are not there. "Common sense" is not part of this question because its a trick question in a way. People that get it right are people that think quickly and read only whats there, and have some understanding of mechanical things to realize that a cannon ball fired straight up does in fact travel the farthest, even if it lands only 1 yard from where it starts. Thats the whole point of this question, seperate the people that read into things and others that read the question and answer it. The whole test is chuck full of different questions like the one we are talking about, each one highlights different types of thinking people. The same test can, in theory, be given to almost every applicant, no matter if they are interviewing for president of the company, an engineer or a janitor. The key is, an optinum canidate for any of those jobs will answer the different questions differently, again that is the point of giving a test, to see if people fit the standard for the job they are applying for. Get it?

Maybe I didnt explain it well but thats the reason for these tests, because certain people tend to excell at certain types of jobs so they devised a test to see if the applicant scores well on the questions that are important to the job. The other questions dont matter.

In any event, just because I know the correct answer and why these tests are given (or were given, they are kind of a thing of the past now) has nothing to do with my deer rifle, nor any common sense I have. It just shows that I have talked to people that have taken these tests and people that worked in HR and explained them. And thats the trick to these tests, every one of the questions is a trick in some way, trying to get people to answer the question so it brings out their personal thought process. The employer can then chart out how the different applicants rank and pick the one they want (usually to bring back for a second or even a third interview). If you are applying for a job now, dont worry about the questions, pop a couple downers so you are cool as a cucumber. If you can be smooth in front of the interview panel, you are in. At least thats what I have been seeing in recent years.
 

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