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3 years ago

Which of the following statements are true about measurements and units?

1 answer:

3 0

<span>A. In the SI system, unit prefixes are used to indicate powers of ten --> TRUE
The prefixes are used to indicate powers of ten: examples are kilo (k), which indicates </span> $10^3$ , or mega (M), which indicates $10^6$ .<span>

B. The unit of length in the SI system is the meter --> TRUE
Lengths are measured in meters in the SI system.

C. Measurements must include both numbers and units --> TRUE
Every measurement must include the number and the unit. Example: for a length, we must write L=10.0 m, where 'm' refers to 'meters'.

D. The SI unit system is used only in Asia --> FALSE
The SI system is used in the whole world.</span>

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What is photographic film

Vesnalui [34]

Answer: its a strip of transparent film, one side coated with gelatin emulsion containing microscopically small light-sensitive silver halide crystals

Explanation:

3 0

3 years ago

A single insulated duct flow experiment using air operating at steady-state is performed in a lab. One measurement location (Sta

weqwewe [10]

Answer:

a) -0.0934 kJ/kg. K

b) The direction of flow is from right to left.

Explanation:

A free flow diagram of the horizontal insulated duct is as shown below.

NOW,

Let assume that the direction of flow is from left to right and consider the following relation for the entropy rate balance equation for a control volume as:

$\frac{\sigma_{cv}}{m}= (s_2-s_1) \geq 0 \ \ \ -------> \ \ \ 1$

Now; if the value for this relation is greater than zero; then we conclude that our assumption is correct.

If the value is less than zero; then we conclude that the assumption is wrong.

Then, the flow is said to be in the opposite direction

Formula for the change in specific entropy can be calculated as:

$s_2-s_1 = s^0(T_2) - s^0(T_1)-R \ In ( \frac{P_2}{P-1}) \ \ \ -------> \ \ \ 2$

where;

$s_1, s_2 , s^0(T_2), s^0(T1)$ are specific entropies

R = universal gas constant

$P_1$ = pressure at location 1

$P_2$ = pressure at location 2

We obtain the specific properties of air at temperature at $T_1$ = (67°C + 273)K = 340 K from the table A-22 ( Ideal gas properties of air)

$s^0(T1)$ = 1.8279 kJ/kg.K

We also obtain the specific properties of air at temperature $T_2$ = 22°C + 273) K = 295 K

From the table A- 22

$s^0(T_2)$ = 1.68515 kJ/kg . K

R = $\frac{8.314 kJ}{28.97 kg.K}$

$P_1 =$ 0.95 bar

$P_2 =$ 0.8 bar

Now replacing our values into equation (2) from above; we have;

$s_2-s_1 = s^0(T_2) -s^0(T_1)-R \ In (\frac{P_2}{P_1} )$

$s_2-s_1 = 1.68515 -1.8279-\frac{8.314}{28.97} \ In (\frac{0.8}{0.95} )$

$s_2-s_1 = 1.68515 -1.8279+ 0.0493$

$s_2-s_1 =-0.0934 \ kJ/kg.K$

Equating our result to equation (1)

$s_2-s_1 \geq 0\\-0.0934 \leq 0$

Therefore , our assumption is wrong and the direction of flow is said to be from right to left.

We therefore conclude that the direction of flow is from right to left.

3 0

3 years ago

If you had 8 balls and 7 of them were a certain weight, and 1 of them was heavier, how could you find the heaviest ball. All the

dybincka [34]

Answer:

There are two method of comparing the balls 1) using a balance 2) by only 2 weighings.

Explanation:

There are two method of comparing the balls 1) using a balance 2) by only 2 weighings.

Make the following groups - --- (1,2,3),(4,5,6),(7,8)

Step 1. compare the Weigh (1,2,3) and (4,5,6)

there are 2 possible outcomes:

1---both the group are of same weight. and named as (Case A)

2--- one of the group is heavier than other and named as (Case B)

Step 2. Let examine both case

In Case A --in this case, now compare the weight of 7th and 8th ball. By this you have recognize the heavier ball by 2 weighing method.

In Case B -- considered the heaviest group (assume group (1,2,3) is heavy), from this group take randomly two ball and compare the their weight. out of these two ball, one is heavy else the third ball is.

7 0

3 years ago

If you want to know how energy will move between two objects, what do you need to know about the objects?

Inessa [10]

You need to know how much friction that object.

8 0

3 years ago

What happens in the crushing can experiment?

Dafna1 [17]

Explanation:

When hot water is poured on the can in a bucket of cold water, the can crushes off means it gets unshaped

7 0

3 years ago