Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.physics > #641834

Re: Mechanical Leverage

Show all headers | View raw

On Sat, 22 Jul 2017 15:43:58 +0000, Boris wrote:

> 
> Hmmm...I've never seen that formula.  That would be E = mass x 
> acceleration x distance moved.
> 

That's correct, although the term "work" is usually used with
this equation rather that "energy," but work is the same as
energy.

This equation demonstrates intuitively that the same amount
of work can be achieved in different ways. 

> 
> What is it about the distance from the fulcrum that is so important?
> 

The above equation does not strictly apply to the lever.  Because
we are essentially rotating about a fixed point, the fulcrum, 
rather than moving things in a straight line, the ideas of "angular
momentum" and "torque" come into play.  This may be a little less
intuitive because now, instead of linear distance, we are rotating
things through angular distance about an axis.

The new, but totally equivalent, equation is now:

Work (energy) = Torque * angular displacement

In the case of the lever, the angular displacement is just s/d,
where d is the lever arm (distance to fulcrum) and s is the
circular arc length.

But Torque = Force * d, so the equation reduces to:

Work = Force * d * angular displacement = Force * s

Thus, we see that the two equations are identical.

The problem may be see how the concept of torque arises,
but this requires elementary vector analysis and may not
be that intuitive.

Back to sci.physics | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Mechanical Leverage Boris <nospam@nospam.invalid> - 2017-07-21 20:48 +0000
  Re: Mechanical Leverage Double-A <double-a3@hush.com> - 2017-07-21 13:56 -0700
    Re: Mechanical Leverage Boris <nospam@nospam.invalid> - 2017-07-21 20:53 +0000
  Re: Mechanical Leverage "F. Russell" <fr@random.info> - 2017-07-21 22:16 +0000
    Re: Mechanical Leverage Boris <nospam@nospam.invalid> - 2017-07-22 15:43 +0000
      Re: Mechanical Leverage "F. Russell" <fr@random.info> - 2017-07-22 17:22 +0000
      Re: Mechanical Leverage "F. Russell" <fr@random.info> - 2017-07-22 23:59 +0000
  Re: Mechanical Leverage "F. Russell" <fr@random.info> - 2017-07-23 00:07 +0000
    Re: Mechanical Leverage James McGinn <jimmcginn9@gmail.com> - 2017-07-22 17:24 -0700

csiph-web