Why don't scissors follow the law of the lever?

[bob_2]

So - It’s the centre of percussion, modified by the bending moment or vibration of the bat or racquet? I had never heard of the centre of percussion before.

From RaffArundel’s link.

[Chronos]

I’d never heard the term before. I’ve done a few problems involving it, but they never reified that point, just asked “where must the rod be hit to ensure no normal force at the pivot point?”, or the like. It never occurred to me that such a point would be relevant to baseball, but in retrospect, of course it would.

[Joey_P]

@Joey_P

How do you figure? The bat is:
A)largest at the end, therefore having more physical contact with the ball
B)Moving the fastest at the end so it has the most momentum.
C)Heaviest at the end, also contributing to it having the most momentum.
D)The circle/path it creates is the shallowest at the end…that is, the bat and the ball will stay in contact for the longest time when the ball hit the bat near the end, giving the bat more time to transfer it’s energy to the bat, it also gives the ball the best chance of going straight.

I’m not quite sure I understand the question. It could be that you and I aren’t on the same page about the term ‘maximum impact’.

@bob_2

a) This is not true at all.
b) Correct, so why is the optimum strike point nearrer the fulcrum
c) Not true.
d) Again wrong - See (b)

If the end of your baseball bat isn’t the largest and heaviest, you’re either holding it upside down or using one that I’m not familiar with.

wait…upon some re-reading…
If you were asking why it’s a few inches (don’t know how many) down from the end, as opposed to near your hands or in the center etc, then I misread/misunderstood your post.
There’s been so many odd questions in this thread…why wouldn’t someone ask why they shouldn’t use the skinny part of the bat near their hands?

Anyway, as mentioned, I’m sure it just gets down to the exact physics of it. Just because the far end may have the most momentum, doesn’t mean it’s optimal since their may be other factors at play. Also, if you attempt to hit the ball 6 inches from the end and you’re a little off, you’ve got some room for error. If you try to hit it as close to the end as possible and you’re off by a half inch, you’re looking at a foul or strike.

[bob_2]

I now wonder if this isn’t relative to a problem I had at work a while ago:

I had to lift a machine that was, essentially, a beam around 20’ long and weighing 2 tons but was not very strong (in normal use it was supported by 8 legs).

I needed to attach slings to the correct points along the length to minimise distortion when lifted by a single hook on an overhead crane and, lacking the maths, decided that points around 4’ in from each end looked about right. It worked and although there was some flexing, the machine survived undamaged. I was not aware of the SD then or I would have asked here.

[Isilder]

@running_coach

The end of the stick is moving faster. Delivers more skull-crushing force.

F=mA.

You need Skull crushing Speed… you’d not get the required force by moving it slowly.
Its the sudden stop at the end that increases the force to do damage.

you might think that you can increase the force from an impact by making the stop more sudden but the amount of damage done is limited by the kinetic energy in the impact. More kinetic energy means it can do more damage, if force is sufficient, and anyway you get higher kinetic energy from higher speed, which therefore means higher forces, all other things being equal.