Question

A thin rectangular plate of uniform areal density σ = 2.79 kg/m2 has length of 37.0 cm and width of 23.0 cm. The lower left hand corner is located at the origin, (x,y)= (0,0) and the length is along the x-axis.

(a)There is a circular hole of radius 8.00 cm with center at (x,y) = (12.50,9.50) cm in the plate.

(b)Calculate the mass of plate.

For part (a) I got 1.81*10^-1 kg

Now for part b I cant quite solve it.
thanks!



Calculate the distance of the plate's CM from the origin.

Answer 1

mass = 2.79(.23*.37-pi(.08)^2)
= 2.79(.0851-.0201) = 2.79 * .065
= .181 kg agree

moment in x (forget the 2.79 density)
.065 x = .0851*.37/2 - .0201*.125
.065 x = .0157 - .0025 = .0125
x = .192 meter = 19.2 cm
now do y of cm the same way

Answer 2

what is the .065??? same for y .065???

Answer 3

.065 is the area of the plater with the hole removed