This video is part of a series of videos presenting solutions of problems related to the machine dynamics topic.
This video presents the solution of problem dealing with the determination of mobility of a given mechanism.
In this problem we are asked to determine the mobility of the mechanism shown here.
First, recall that the mobility, M, of a mechanism is equal to
Three times L decreased by 1 minus twice j 1 minus j2
Where
L is the number of links in the mechanism, L is the number of mechanical parts in the mechanism.
J 1 is the number of lower pairs, it is the number of kinematic pairs that allow, each, one degree-of-freedom.
And
J 2 is the number of higher pairs, it is the number of kinematic pairs that allow two degrees of freedom, each pair.
Here the mechanism is made of 4 links:
the ground,
One bar,
And, two sliders.
Thus, L is equal to 4
The lower pairs here are rotating joints, and translating joints.
There are two prismatic pair connecting each slider to the ground.
There are two pin or rotating joints between each slider to the bar.
In all there are four lower kinematic pairs allowing each one degree-of-freedom.
In this mechanism, there is no higher pairs.
All connections are either rotating pairs or translating pairs, which are lower pairs.
Thus, j 2 is equal to 0
Finally, mobility is equal to
3 times 4 minus 1
Minus 2 times 4
Minus 0
Which is equal to 1.
Hence, the mobility here is equal to 1
The mechanism has one degree-of-freedom.
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