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Discussion Starter · #1 ·
The post on the Tiki bar has gotten me thinking. There are so many ways to view something (i.e. which direction you measure an angle, is the glass half full or half empty, is that an uphill run or downhill, etc.) A lot of times the ways of looking at something are the easy way, and the way overengineered way. SO for fun here's the question.

A few years back in a Fundamentals of Materials class the instructor asked us the following question. We debated for about an hour or two with huge answers of coefficent of friction, gravity, yada, yada, yada. When we were done he gave us a very simple answer to counter our very indepth answers. And now for the question (many of you have probably debated this one in school at some time).

According to the laws of physics every action has an equal and opposite reaction, so if a horse is attached to a cart, how does it go anywhere? If the cart expresses x amount of force down and is countered by x amount of force upwards, and the forward force is countered by a rearward force, how can the cart move?

pbm
74 cj5,304,t18,2.46 ts d20,30f,44r,soa,MORE buggy front,35's,Rci's,5pt,full cage,air,etc.
78 J10,360,727,d20,44f,44r,35's,4" lift,etc.
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Just say ( giddyup) It'll move if the horse aint deaf!!!

It's as close to a 1ton as it can get and still be a jeep!!! Gotta love it!!
 
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something to do with the round wheels I imagine.

/wwwthreads_images/icons/cool.gif 84 cj7 Laredo /wwwthreads_images/icons/cool.gif Superior 1 piece, more to come...../wwwthreads_images/icons/smile.gif
 

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According to the laws of physics every action has an equal and opposite reaction, so if a horse is attached to a cart, how does it go anywhere? If the cart expresses x amount of force down and is countered by x amount of force upwards, and the forward force is countered by a rearward force, how can the cart move?

Never heard it before, so here is my answer.

The cart will not move so long as the forces are equal. For it to move, one force must dominate above the others and upset the equilibrium.

JEEPN
Winter Harbor, Maine
'81 CJ-8 Scrambled, It's a Jeep, Chevy, IHC kinda thing!
'88.5 Zuki, 5" Calmini, Locked, Swamped, Rolled, and just generally broken in right!
 

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smack the horse in the arse... and it'll move for awhile... and at a rapid rate..

http://www.jeepgod.net

84 CJ-7 401/T-18/D20/D44/D60w/4.10&Detriots/YJ frame & tub/35x16x15 Boggers
survival is instinct, but living takes guts
 

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Horse/cart combo reacts against ground. Horse is usually deaf so kick in arsh reaction comes into equation. Counter reaction to kick (or horse kick) usually throws you back smack middle of horse poop pile. Pile reacts to your weight, flies all over your buddy nearby. Now buddy kicks you in the arsh and the whole thing starts all over again illustrating yet another law of physics: energy is not lost just changes or being passed on. (rough translation from greek to german to hungarian to hunglish to english)


'91 YJ,I-6,2.5" lift,Boomerangs,33s,D30,D35c,Lock-Rights F&R
 

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Simple, Horses feet move backwards 2 feet with, say, 100lb/ft of torque. This in turn moves the horse and cart forwards 2 feet (provided the cart does not have a rolling resistance of greater than 100lbs)

 

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I hated physics back in college and I hate physics today. So, I'm going to do the same thing that I used to do... try to look at my neighbors paper or guess at the answer if I can't see it.
I'll guess it has something to do with the amount of work or energy that the horse does and some of this work being converted into heat energy(wheel bearings).
Now this is the point where you say WRONG you dumbass and give me a zero./wwwthreads_images/icons/wink.gif
Somebody refresh my memory, do the forces on a moving object still add up to zero?

80 CJ7 258 T176
36X12.5 Swampers
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Discussion Starter · #11 ·
Naw, I wont call you a dumbass, I admit every once in a while I participated in 'group test taking'. I just realized I rely on computer things way to much to think of stuff I already know. So I thought I'd share a little mind exercise with everyone.

pbm
74 cj5,304,t18,2.46 ts d20,30f,44r,soa,MORE buggy front,35's,Rci's,5pt,full cage,air,etc.
78 J10,360,727,d20,44f,44r,35's,4" lift,etc.
Support Search and Rescue.......Get Lost!
 

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Discussion Starter · #13 ·
I must have been on the computer too long today (actually on it all day) but I thought that was really funny /wwwthreads_images/icons/smile.gif

pbm
74 cj5,304,t18,2.46 ts d20,30f,44r,soa,MORE buggy front,35's,Rci's,5pt,full cage,air,etc.
78 J10,360,727,d20,44f,44r,35's,4" lift,etc.
Support Search and Rescue.......Get Lost!
 

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Good one Brad. I like it.

JEEPN
Winter Harbor, Maine
'81 CJ-8 Scrambled, It's a Jeep, Chevy, IHC kinda thing!
'88.5 Zuki, 5" Calmini, Locked, Swamped, Rolled, and just generally broken in right!
 
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Who cares? Who still uses a horse drawn carriage anyway, other than the Amish folks up in PA!? Just kidding, it's really a good question. I'll go with "D" - all of the above.

canis
'82 CJ-7/360/727/D300/cobra, M.O.R.E. shackles, 1/2" steel bumper, 1" body lift and lots of ideas!

'96 ZJ - 4.0L/42re/np242/optima/cobra and other goodies
 

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Forget about the upwards force (earth against the wheels) and downwards force (mass*gravity) as they're equal there is no vertical motion. We'll neglect friction, too, and assume the horse has no mass. The horse applies a force to the cart; this force divided by the mass of the cart causes the cart to accelerate (force=mass*acceleration).

However, the horse's feet are applying a force against the earth; since no force is required to accelerate the weightless massless) horse, the force against the horse's feet is equal and opposite to the force the horse is exerting on the cart. Since the horse is exerting this force on the earth, the earth must accelerate in the opposite direction-- but since the mass of the earth is so great, the acceleration will be very small.

Normally, we define our frame of reference as fixed with respect to the earth, so only the horse appears to move..... but we could just as easily define the frame of reference as fixed with respect to the horse, so only the earth is seen to move.

-Dana

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government. - Thomas Jefferson
 

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hunglish... I like it /wwwthreads_images/icons/smile.gif

Congrats new Papa. What's that in Hunglish?

'86 CJ7/AMC 360/TR Ignition/T999/D300/OEM D44 rear.../wwwthreads_images/icons/cool.gif
 
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The forward force is greater than the resistance offered by the cart. The system is not in equilibrium when the horse is moving, it changes from a static system to a dynamic system. The difference in resistance between the cart and the horse is converted to forward motion. Make the cart really heavy, and put it on a steep hill, and then see who pulls who/wwwthreads_images/icons/wink.gif.

Cage Up, Wheels Down
Jeepfiend
All my Jeeps are in pieces!
 
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sounds like a muffler bearing question does it not ?????????????????????d.s

80toy welded 5.29 6.5 lift 22r 5 sp want dual t cases cage in the mail tsl 33,s 100qt cooler & big ass rotweiler in bed
 
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