Weight question

[drewyallop]

You are standing upright on two force plates, weight distributed equally. You bend your knees.

Does the force on the plates increase or decrease?


Drew

 

[SteveT]

How much do you bend your knees ....

 

[macduffer]

If you bend your knees quickly (ish) you will reduce the force downwards, because your body weight is being allowed to bend your knees rather than push straight down through fixed limbs into the plates.

 

[SteveT]

macduffer ... are you suggesting there is a 'dynamic' weight as well as a 'static' dead weight ...

 

[Dariusz J.]

You are standing upright on two force plates, weight distributed equally. You bend your knees.

Does the force on the plates increase or decrease?


Drew

If you mean the scenario similar to e.g. preparing to jump - it will decrease, because the weight decreases.

Cheers

 

[macduffer]

I'm not suggesting there's more than 1 'type' of weight, I'm talking about the force exerted on the plates by your body is transmitted. When you stand with your knees locked (for argument's sake) then the mass of your entire body above those joints is pushing down through them, which in turn exerts force on the plates.
If you bend your knees, then that force is (temporarily) relieved from the plates. Your 'weight' doesn't change.

Stand on a pair of scales and try it.

 

[Dariusz J.]

The weight changes. When changing the CoM vertically an additional acceleration (acting either in the same direction as gravity or in the opposite one) your weight must change adequately which can be observed on the scales. What always remains unchanged is mass.

Cheers

 

[macduffer]

What always remains unchanged is mass.

Cheers

You're absolutely right, Dariusz. (Though You'll notice I used 'weight' in inverted commas, to respond to SteveT's comment, which used the term)

 

[SteveT]

Hey, macduffer .... What about exerting additional thrust to the force plates so that the sum of the R and L measurement is greater than your total dead weight .. ya think ..??!!

 

[spktho]

This discussion might get there--in general lighter on the back swing, heavier on the down swing, lighter at impact.

 

[macduffer]

Hey, macduffer .... What about exerting additional thrust to the force plates so that the sum of the R and L measurement is greater than your total dead weight .. ya think ..??!!

On the way 'back up', yup.

 

[SteveT]

On the way 'back up', yup.

Foot "tumble" ..