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# Mechanics 2 - Centre of Mass Watch

1. A standard lamp consists of a uniform heavy metal base of thickness 4cm, attached to which is a uniform metal rod of length 1.75m and mass 0.25kg.

What is the minimum mass for the base if the centre of mass of the lamp is no more than 12cm from the ground?

I end up getting 1.94kg whilst the answer in the book says 1.99kg.

My working: (0.895 x 0.25) + (0.02m) = (0.12(0.25+m))

Moments taken from the base of the lamp

Thanks
2. (Original post by Quido)
A standard lamp consists of a uniform heavy metal base of thickness 4cm, attached to which is a uniform metal rod of length 1.75m and mass 0.25kg.

What is the minimum mass for the base if the centre of mass of the lamp is no more than 12cm from the ground?

I end up getting 1.94kg whilst the answer in the book says 1.99kg.

My working: (0.895 x 0.25) + (0.02m) = (0.12(0.25+m))

Moments taken from the base of the lamp

Thanks
In red, is incorrect. You may find a diagram useful, if you haven't already drawn one.
3. (Original post by ghostwalker)
In red, is incorrect. You may find a diagram useful, if you haven't already drawn one.
Ah right, I was only adding half the distance of the base, 0.02 instead of 0.04. Thanks for the help

Updated: October 17, 2016
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