# Calculate Mass Of Shaft and Hollow Shaft

#### febbie22

Hi, i have a shaft with OD = 33.40mm Wall Thickness = 3.38 mm length = 2.4m

Density of shaft = 2750

The weight per unit length that is given is 0.8555 kg/m

My question is how did they get it as im using the volume formula for a cylinder which is

V=Pie*h(R^2 - r^2) then i times this by the density 2750 to get the mass but i get

1.111 which then divided by 2.4 would be 0.463.

Where am i going wrong.

Thanks for any help

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#### Shaun_W

Check you're using the correct numbers, and remember that the inner diameter is the outer diameter minus twice the wall thickness. That caught a few folks in my class out.

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