Answer: Manholes are usually round, primarily because roundness is the best shape to resist the compression of the earth; covers are round because they are easier to manufacture than square or rectangular shapes, they are easier to move by rolling, and they can't fall into the opening.

Explanation:

7 0

3 years ago

In which situation is it better to have low friction?

Ray Of Light [21]

A student walks down a hall I’m pretty sure

7 0

3 years ago

A powder sample weighing 250 g and having a surface area of 1 m2/g is dispersed in 1 L of water. After 10 minutes, 0.4 g of the

lisabon 2012 [21]

Answer:

$K = 2.64 * 10^{-8}$

$15 \frac{5}{8}$ hours

Explanation:

Given

Surface Area (S) of 250 grams of powder sample $= 250$ square meter.

$S = 2500000$ square centimeter

$V\frac{dC}{dT} = 0.40$ grams/minute

$V\frac{dC}{dT} = \frac{dM}{dT} = \frac{0.40*60}{10} = 0.66$ mg per second

$C_s = 0.01$ gram per cubic meter $= 10$ mg/ml

$\frac{dM}{dT} = K SC_s$

$0.66 = K* 2500000* 10\\$

$K = 2.64 * 10^{-8}$ cm /sec

b) Time taken

Time taken to sink

$\frac{10*60}{0.4} * 37.5 = 56,250$

Time in hours

$15 \frac{5}{8}$ hours

6 0

3 years ago

Why calcium is more reactive than<br>magnesium?

miskamm [114]

Answer:

Ca is more reactive because it has a lower

ionization energy than Mg. This is because it is lower in the periodic table. The added central electrons added over the extra period provide shielding in the center of the atom

4 0

3 years ago

Read 2 more answers