I know torque= radius x force
thus if i want to loosen a bolt the longer my wrench the more torque i exert.

I was thinking though how does this obey the conservation of energy principal?
E= integral (force*dx)
x=distance

As it seems like I have to exert a lot more force if i use my fingers to stubbornly loosen the bolt while with a 1 foot long wrench the effort seems minimal.

2/2/2008 5:03:03 PM

Maybe it's because your fingers travel a much smaller distance x because the radius is smaller.



Say, you turn a bolt with your fingers with 10 lbs of force for only 1 inch. Well, maybe you only need to exert 2 lbs on the wrench, but now your exerting that force over 5 inches instead over 1 inch. The same work is done

i.e.
Case 1= 10lbs* 1 inch= 10 in-lbs

Case 2= 2lbs* 5inch= 10 in-lbs

but you've exerted 2 different forces with the same resultant work

[Edited on February 2, 2008 at 5:21 PM. Reason : over]

2/2/2008 5:20:41 PM

2/2/2008 5:42:03 PM

i love angular momentum.

2/2/2008 6:02:02 PM

i like the word tangential

2/2/2008 6:09:39 PM

Quote :

"As it seems like I have to exert a lot more force if i use my fingers to stubbornly loosen the bolt while with a 1 foot long wrench the effort seems minimal."

?

t = rF

the longer the lever (r) the less force required (F) to create the same torque

2/2/2008 6:24:46 PM

what is confusing didnt you answer your own question

2/2/2008 7:40:53 PM

oh i was thinking the distance was the distance the bolt physically rotates not the position to which the force is applied.

2/2/2008 8:08:29 PM

"distance" is the distance that the force acts through

2/2/2008 8:46:51 PM

Quote :

"I was thinking though how does this obey the conservation of energy principal?"

well last time i checked, the units of torque and the units of energy were the same

(J for energy which is just N*m and torque is a m*N in SI, same shit)

2/2/2008 8:58:15 PM

boy this sure is a stupid thread

2/2/2008 11:38:56 PM

nahh i had to do something for work with a torque screw and couldnt figure some shit out

2/3/2008 12:52:39 AM

Quote :

"well last time i checked, the units of torque and the units of energy were the same (J for energy which is just N*m and torque is a m*N in SI, same shit)"

it's not that simple...torque and energy are not interchangeable.

2/3/2008 8:50:37 AM

yes they are

if the units are the same they are interchangeable

they have to be...thats one of the underlying principles of dimensionality

2/3/2008 11:45:29 AM

Well, it's not quite that simple. Energy is a scalar quantity, whereas torque (r X F) is a vector. An analogy that might be helpful is speed and velocity. Same units, but not strictly interchangeable.

Maybe Wikipedia can help, too.

http://en.wikipedia.org/wiki/Torque#Units

2/3/2008 1:53:45 PM

Are you majoring in MAE? If so, its going to be a looong road for you

2/3/2008 5:27:15 PM

Quote :

"yes they are if the units are the same they are interchangeable they have to be...thats one of the underlying principles of dimensionality"

torque is a force on a lever arm about an axis and is a static measurement. Torque is simply an angular force which can be converted to a linear force at a distance from the axis. Energy (Work) in a linear sense is force times the distance over which the force is exerted on a moving object. The two are not the same, no matter what you try to assume from the units.

[Edited on February 3, 2008 at 6:18 PM. Reason : there's also angular work, but that's another topic]

2/3/2008 6:16:55 PM

don't worry, he's majoring in cash. the only place he might need an understanding of torque is that posterior physics class to get his minor in ass.

2/3/2008 6:18:02 PM

Quote :

"torque is a force on a lever arm about an axis and is a static measurement. Torque is simply an angular force which can be converted to a linear force at a distance from the axis. Energy (Work) in a linear sense is force times the distance over which the force is exerted on a moving object. The two are not the same, no matter what you try to assume from the units."

you basically just pwnt yourself here

work is force over a distance linearly

torque is force over a distance in the angular direction

they are the same thing

think about it..how do you remove a lug nut? you apply force over a distance (rotation in this case) to over come the force of friction

how do you carry a box? you apply force over a distance picking it up opposing the force of gravity

[Edited on February 3, 2008 at 6:38 PM. Reason : 

2/3/2008 6:35:31 PM

First this guy says torque is the same as energy, then he says it's the same as work. What a tard.

2/3/2008 10:33:07 PM

Torque is an angular force, not work. The force you put on the lever arm over the arc length turned to loosen the lugnut is work. If the lug nut is stuck and you put 100 lbs of force at a distance of 1 foot, the lug nut does not move, you have not exerted any work. A force yes, and a torque of 100 ft-lbs but no work has been done.

You push a box 1 ft. across the floor with 100 lbs of force, you have done 100 ft-lbs of work, but have not exerted any torque on the box. Torque and work are not the same and cannot be interchanged as such. If you don't understand that, you should go re-read statics and dynamics books.

2/3/2008 10:56:43 PM

T = F x r

W = F x d

same damn thing, different co-ordinate systems

you guys have it all wrong

Quote :

"irst this guy says torque is the same as energy, then he says it's the same as work. What a tard."

energy and work are equivalent J = N*m

[Edited on February 3, 2008 at 11:08 PM. Reason : 

2/3/2008 11:06:57 PM

so, work is the same as energy, which is the same as torque?

that's hilarious

i hope you aren't an engineer

2/3/2008 11:14:54 PM

you are all wrong guise

they are the same thing

2/3/2008 11:20:11 PM

http://en.wikipedia.org/wiki/Torque#Relationship_between_torque.2C_power_and_energy

2/3/2008 11:44:36 PM

at this point you're probably just trolling, but if torque and work were the same, there would be no reason to rate engines for both horsepower and torque.

2/3/2008 11:49:33 PM

dude

srsly power is work per time and torque is work

what are you thinking

2/4/2008 12:31:42 AM

I'm glad you think so

2/4/2008 6:11:59 AM

Work is scalar and torque is vector, period.

however

Quote :

"at this point you're probably just trolling, but if torque and work were the same, there would be no reason to rate engines for both horsepower and torque."

is pretty silly considering HP and torque dont have the same units to begin with and thus that statement doesnt make much sense.

2/4/2008 8:47:04 AM

no work is a vector too

2/4/2008 9:20:11 AM

no, it is not.

edit: yes its obvious youre trolling but i felt like answering anyways

[Edited on February 4, 2008 at 10:05 AM. Reason : ]

2/4/2008 10:01:55 AM

Quote :

"is pretty silly considering HP and torque dont have the same units to begin with and thus that statement doesnt make much sense"

I was making the point that work and torque were not the same, as did you with that statement...units are irrelevant.

2/4/2008 11:58:36 AM

dude i can draw a picture showing that work is a vector

it is directionally dependent

if you cant see that you are the one that needs to not be an engineer

2/4/2008 1:55:10 PM

lol, its a little old now.

2/4/2008 3:26:57 PM

dude got owned and tried to play it off like he was trolling?

wow. wtg guy

2/4/2008 5:12:27 PM

well im not sure who you are referring to ^ and its sure hard to tell if people are trolling or not on these boards. but i sure hope Aficionado is trolling.



[Edited on February 4, 2008 at 5:39 PM. Reason : ]

2/4/2008 5:30:07 PM

So basically if a giant turn table spins with enough torque, and helicopter sitting on top of it will take off, right?

2/4/2008 11:12:59 PM

basically

it is the opposite reason why the airplane didnt take off

2/5/2008 10:48:13 AM