Change in Acceleration: Analyzing Force Time Curve

[david smith]

All

If I stand on a force plate it will measure a force in Newtons equivalent to my mass X acceleration due to Gravity, let's say that is 1000N. If I displace the mass vertically (and I'm only interested in force normal to the force plate) then there will be a change in the force applied.

Again if I roll across the force plate on a roller skate then a force is applied and the force /time curve characterised will be flat because there is no displacement of the mass vertically.

So my question is if there is always an acceleration due to gravity then does the acceleration due to vertical displacement of the mass represent a change in acceleration or a change in velocity. Which is the more correct term?

This change in acceleration or velocity can be characterised on a computer screen as a force time curve. As the mass is constant then the curve actually represents a change in acceleration. If the curve were a straight line slope then this would be a change in velocity i.e.
acceleration but as the line is curved then this represents a change of acceleration over time.

Is this correct?

Cheers Dave Smith

 

[sophiecentaur]

The force plate will measure the force, which will be mass times acceleration. If there is no change in velocity there will be no acceleration and no change in measured force. Imagine an arrangement which consists of a crane, also mounted on the force plate. If the crane is lifting the mass at a steady speed, the force plate will record the same value as when the mass is hanging, stationary, on the crane. Whilst starting or stopping, however, there will be a change in 'apparent weight' - i.e. force on the plate.