Re: Levers increase force?

jbriggs444 wrote:
On Dec 23, 9:25 am, Peter <Poakfi...@xxxxxxx> wrote:
On Dec 22, 9:18 pm, Sam Wormley <sworml...@xxxxxxxxx> wrote:





On 12/22/09 7:47 PM, Peter wrote:
On Dec 22, 8:39 pm, Sam Wormley<sworml...@xxxxxxxxx> wrote:
On 12/22/09 6:59 PM, Peter wrote:
On Dec 22, 6:53 pm, Sam Wormley<sworml...@xxxxxxxxx> wrote:
On 12/22/09 4:57 PM, Peter wrote:
Force F = ma; the force that gives a mass m an accelerations a, and
the force that gives a mass 1000m an acceleration a/1000, are equal,
because ma = 1000m(a/1000)l, no?
Did you look over:
http://hyperphysics.phy-astr.gsu.edu/HBASE/Mechanics/lever.html
Yes, I did. It seems they have it wrong there.
Can you articulate the section that is wrong, for my benefit?
Thanks.
"With a lever, one can obtain a multiplication of force,"
That is not correct.
Let me put back a little context, "The lever is one of the
so-called "simple machines" from which many more complex
machines are derived. With a lever, one can obtain a
multiplication of force, but of course not a multiplication
of energy. The multiplication of force can be seen to arise
from the equilibrium of torques..."
I refer the reader to the accompanying diagram at
http://hyperphysics.phy-astr.gsu.edu/HBASE/Mechanics/lever.htmlhttp:/...
Peter, I would recommend getting a crowbar and dismantling something
with it, thinking about the amount of force exerted at the short end.
You do know what force is, do you not?- Hide quoted text -
- Show quoted text -
Sam, force equals mass times acceleration, by definition, i.e., F = dp/
dt = ma.

No. That is not correct. That's not what Newton's second law states.

Newton's second law says that

F = ma

Where F is the TOTAL force on an object
and m is the mass of that object
and a is the acceleration of that object's center of gravity.

You don't get to point at a single force, call it F and say that F=ma
for that
single force acting alone.

<snip> Nitpick. That's why the simple algebraic expression, F=ma,
is not quite correct, and is confusing to non-physics types.
Sigma should be mentioned or something when writing the equation.

/BAH
.

Relevant Pages

  • Re: Cheap Access to Space
    ... Do we mean inertialess acceleration? ... conventional spacecraft. ... equipped with a rocket, accelerates away - so that the spacecraft ... I believe negative mass to be impossible. ...
    (sci.space.policy)
  • Re: Cheap Access to Space
    ... Do we mean inertialess acceleration? ... conventional spacecraft. ... equipped with a rocket, accelerates away - so that the spacecraft ... I believe negative mass to be impossible. ...
    (sci.space.policy)
  • physic lab assignment can you help me??
    ... The Relationship Involving Acceleration, Net Force, and Mass Lab ... How does the acceleration of a cart depend on the resultant ...
    (sci.physics)
  • Re: Falling Down
    ... which were supposed to explain that the mass of the ... It does not make sense to me that the mass of the earth affects the ... rate of falling (so that a coin would fall faster on earth than on the ... this does not mean that the observed acceleration ...
    (sci.physics)
  • Re: PD has questions about science. Can any of you help?
    ... acceleration, which matches the direction of the force." ... Double the mass and the acceleration ... Obviously a force (in pounds) isn't equal ... Not once in my entire architecture career has calculus ...
    (sci.physics)