Pipe question

Divanhot SG

diagram:

http://img194.imageshack.us/i/60295897.jpg/

question:

http://img149.imageshack.us/i/80731985.jpg/

ThunderFbolt SG

What have you attempted so far? Which part do you not know how to do?

Darkness_hacker99 SG

(a) Vol of Earth removed = Area of trap x length. Answer in cubic metre.

(b) From the understanding. 1m3 of Earth weights 1.8 x 10^3( which is1800kg). To find the mass of all soil removed, use the answer from (a) = xm3 x 1.8 x 10^3.

(c) Calculate % of earth not replace. From understanding, it means the

(vol of pipe/ vol of trench) x 100%.

Vol of pipe = pi r sq x length.

Then substitute in.

*actually there is a short cut method for the more advance*

(d) Flow = 0.8m/s.

How much water are there in 0.8m of pipe?

pi r sq x 0.8m = vol of water in 0.8m of pipe.

If x amt of water pass through every second. Vol of water pass through in 1h = ?

How many seconds are there in 1hour?

Multiple the answer you got previously by the amount of seconds in 1h.

This is my systematic approach.

Divanhot SG

hi darkness hacker bro, like ask for (d) does 0.8m/s flow means in 1 s, there is 0.8m water flowing through the pipe?

also for (d) can we use surface area of cylinder*0.8 to get vol of water, how come use area of circle*0.8 instead?

Forbiddensinner SG

hi darkness hacker bro, like ask for (d) does 0.8m/s flow means in 1 s, there is 0.8m water flowing through the pipe?

also for (d) can we use surface area of cylinder*0.8 to get vol of water, how come use area of circle*0.8 instead?

0.8m/s means water flow through at a rate of 0.8m in a second. Logically speaking, it is correct to say there are 0.8m of water flowing through in a second.

If you uses surface area instead of pi r^2, what you will get is an amount that indicates the amount of water flowing through the pipe on the outside of the pipe, which doesn't make sense at all.

Divanhot SG

i dun understand the concept abt surface area... how come means outside. i thought area means inside.. :(

Forbiddensinner SG

i dun understand the concept abt surface area... how come means outside. i thought area means inside.. :(

Surface area of the pipe means the area of the outside of the entire pipe.

Imagine that the pipe is made of paper, and you cut a line through its middle horizontally, thus allowing you to open it up to become a piece of rectangular paper.

Surface area will means the area you can see now, which is basically the area of the whole paper rectangle.

Darkness_hacker99 SG

(d)

usually, the actual calculation is whole circle minue the internal surface area. but the question didn't state the accuracy of the whole pipe. We'll assume the surface area of the circle is pi r sq.