英文物理題目超難求解?

[匿名]

2015-11-09 9:57 am

a cubical box that has been constructed from uniform metal plate of negligible thickness. The box is open at the top and has edge length L = 29 cm. Find (a) the x coordinate, (b) the y coordinate, and (c) the z coordinate of the center of mass of the box.

回答 (1)

麻辣

2015-11-11 10:59 am

✔ 最佳答案

(a) Find the x coordinate = ?

Bottom face = OBCD

Top face = EFGH

O = (0,0,0)

A = Aera for each face

Left face = OEFB

Right face = DHGC

Front face = BCGF

Rear face = ODHE

x-axis = OB

y-axis = OD

z-axis = OE

x = L/2 = 14.5 cm for symmetric shape

(b) the y coordinate = ?

y = L/2 = 14.5 cm for symmetric shape

(c) the z coordinate of the center of mass of the box.

P = (L/2,L/2,L/2) for left, right, front & rear faces with 4A

Q = (L/2,L/2,0) for bottom face with 1A

ΣM(Q) = 5A*Zbar - 4A*L/2 - A*0 = 0

Zbar = 2A*L/5A = 2L/5 = 58/5 = 11.6 cm

Answer: Center = (L/2,L/2,2L/5) = (14.5 cm, 14.5 cm, 11.6 cm)

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