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Fundamentals of Stress and Vibration
[A Practical guide for aspiring Designers / Analysts] 1. Mathematics for Structural mechanics

[Fig 1.82: weight lifting mechanism on a four wheel cart]

Solution: it can be observed that, the external weight (mg) has a moment, which must be
countered by the moment due to the weight of the cart (W ) and lifting mechanism (W ).
2
1
The major assumptions to compute the moment due to external weight are as follows:

Ø The boom is rigid.
Ø The boom length sufficiently large.
Ø The external weight does not alter the CG of the cart system.
Ø The lifting mechanism is centrally placed on the cart. The CG of the cart and the lifting
mechanism are along the same vertical axis.
Let us use vectors to calculate the moment of the external load.

Moment due to external load = r × mg

QP No. SSC/Q4401, Version 1.0, NSQF Level 7, Compliant with Aero and Auto Industries,
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