A screw jack has a single start thread of pitch 6 mm and an
operating handle of radius 450 mm. The following readings of
load and effort were taken during a test on the jack.
Load (kN) 0 1 2 3 4 5 6 7 8 9 10
Effort (N) 2.2 6.6 11.8 17.0 22.2 27.2 32.2 36.8 41.4 46.9 52.4
(a) Plot a graph of effort against load and from it, determine the
law of the machine.
(b) Plot a graph of mechanical advantage against load.
(c) Plot a graph of efficiency against load and state whether the
machine is likely to overhaul.
(d) Calculate the theoretical limiting values of mechanical
advantage and efficiency, and state whether your graphs
tend towards these values.
(e) Calculate the work input and the work done against friction
when raising the 10 kN load through a height of 50 mm.
I am confused with the work done against friction, Is it same as work done in overcoming friction?
Work done against friction?
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