Law of a Machine :
This is define by the relationship between the
Effort applied to a machine to lift the load.To
Iift different loads various effort to be applie
to a machine.If we take the record of various
efforts required to lift the corresponding loads and plot a graph between load lifted and effort applied then generally it will represent a straight line ----which does not pass through the orgin.
In the intercept OA represents the effort required to overcome the frictional resistance as offered by the machine.
Mathematically , the law of a machine can be
Expressed by the relation :
P = mW + C
Where P = Effort applied to raise the load W
m = tan @ = slope of the line AB
= constant which is known as co- efficient of friction .
C = constant ( which represents the machine friction )
= Intercept OA = Effort required to overcome friction.
This is define by the relationship between the
Effort applied to a machine to lift the load.To
Iift different loads various effort to be applie
to a machine.If we take the record of various
efforts required to lift the corresponding loads and plot a graph between load lifted and effort applied then generally it will represent a straight line ----which does not pass through the orgin.
In the intercept OA represents the effort required to overcome the frictional resistance as offered by the machine.
Mathematically , the law of a machine can be
Expressed by the relation :
P = mW + C
Where P = Effort applied to raise the load W
m = tan @ = slope of the line AB
= constant which is known as co- efficient of friction .
C = constant ( which represents the machine friction )
= Intercept OA = Effort required to overcome friction.
1. Maximum Mechanical Advantage :
Mechanical Advantage of a machine is given by ;
M.A = W/P = Load lifted / Effort applied
From equation, P = mW + C
= mW = P - C
= W/P = 1/m ( 1- C/P)
= M.A = 1/m (1- C/P)
We see that with the increase of load the effort increases. As the effort increases, C/P value decreases ( Since C is constant).
For small value of C/P,M.A of a machine increase as given by equation. So if P is too large then C/P become negligible and M.A of a machine will be maximum.
Maximum Mechanical Advantage = 1/m.
Maximum Mechanical Advantage = 1/m.
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