Question

Mass of bricks is 4,5 kg. Dimensions – 25*12*6,5 cm. What is pressure, when: a)the brick stands on the big side; b)the brick stands on the other side?

Answer 1

a) 1470 Pa
b) I do not understand which of the other faces of the brick to use, so I cannot answer.

Explanation:

The weight of the brick is `m*g = 4,5 kg*9.8 m/s^2 = 44.1 N`.

Pressure is a measure of the concentration of force. In this case, the force is the weight of the brick, so pressure is the weight divided by the area of the contact. The SI unit of pressure is the Pascal, Pa which is equivalent to `N/m^2`. Therefore, we should convert the dimensions to meters. So the brick's dimensions are 0.25 m by 0.12 m by 0.065 m.

a) They are asking for pressure when the brick stands on the big side, so the area of the contact in this case is the product `0.25 m times 0.12 m`.
`pressure" = (44.1 N) / (0.25 m times 0.12 m) = 1470 Pa`

b) I still do not understand what is meant by "the other side". In my experience, bricks are rectangular solids -- with 6 faces. With the brick standing on its big side, the other 5 sides are the top, front, back, left side, and right side. Top and bottom dimensions would be the same. Front and back dimensions would be the same. Left side and right side dimensions would be the same.

So I would think that the "area of contact" for part b would be either `0.25times0.065 " or " 0.12times0.065`.

So I do not understand which of those 2 products is the area to be used. But if you understand, multiply the dimensions of the contact (either of the above choices) and do what I did for part a.

I hope this helps,
Steve