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4 years ago

What does the term atomic number mean?

2 answers:

5 0

The atomic number is amount of protons in an atoms nucleus.

The atomic number will always be shown in the top lefthand corner in the periodic table.

amid [387]4 years ago

4 0

D. the number of protons in an atomic nucleus

That is because the atomic number is the number of protons, which would never change. The neutrons change if their is an isotope.

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List two examples of the following states of matter: solids, liquids, and gases. Please answer in NO LESS THAN 3 complete senten

slavikrds [6]

Answer:

Matter can exist in one of three main states: solid, liquid, or gas. Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around. Liquid matter is made of more loosely packed particles.

Key Takeaways: Examples of Solids, Liquids, and Gases

A solid has a defined shape and volume. A common example is ice. A liquid has a defined volume, but can change state. An example is liquid water.There are four natural states of matter: Solids, liquids, gases and plasma. The fifth state is the man-made Bose-Einstein condensates. In a solid, particles are packed tightly together so they don't move much.

Explanation:

7 0

3 years ago

When a voltage difference is applied to a piece of metal wire, a 8-mA current flows through it. If this metal wire is now replac

DanielleElmas [232]

Answer:

Explanation:

The resistance of a wire can be given by the following expression

$R=\frac{\rho\times L}{A }$

where R is resistance , ρ is specific resistance , L is length of wire and A is cross sectional area

specific resistance of metals are almost the same . So in the present case ρ and l are same . Hence the formula becomes

R = k / A where k is a constant .

The diameter of wire becomes two times hence area of cross section becomes 4 times or 4A .

Resistance becomes 1/4 times . Hence if resistance of metal wire is R , resistance of silver wire will be R / 4 .

current = voltage / resistance

In case of metal wire

8 x 10⁻³ = V / R

In case of silver wire

I = V / (R / 4 ) , I is current , V is potential difference .

I = 4 x V/R

= 4 x 8 x 10⁻³ A

= 32 mA.

6 0

4 years ago

A heat pump that operates on the ideal vapor-compression cycle with refrigerant-134a is used to heat a house. The mass flow rate

Savatey [412]

(a)

Use â€œsaturated refrigerant-134a pressure tableâ€, to find $ , h , and of refrigerant-134a, at 320kPa (P) .

$h_{1} h_{g}$ = 251.93kJ/kg

$s_{1} (s_g}$ ) =0.93026 kJ/kg-K

$v_{1}(v_{g})$ =0.063681 m/kg

we solve $h_{6}$ ,

$h_{6}$ = 282.62 kj/kg

$h_{3} (h_{f)}$ = 127.25 kJ/kg

We use this formula for finding $Q_{n}$

$Q_n} =( h_{2} - h_{3} )$

= 38.8 kw

(b)

Find the COP of the heat pump ( $COP_{R}$ ) .

( $COP_{R}$ ) = $q_{L} /w_{in}$

$COP_{R}$ = (282.62 -127.25) / (282.62-251.93)

= 5.06

What is evaporator pressures ?

Valves for regulating evaporator pressure

Although the compressor suction pressure may be lower, evaporator pressure regulation (EPR) valves can be employed in the suction line to prevent the evaporator pressure from dropping below a set or controlled value.

An EPR valve is used for the following tasks:

1. Prevent potential damage to a liquid chilling evaporator from the liquid freezing.

2. Prevent frost from accumulating on an air-cooling evaporator when it is near freezing point or when operation cannot be interrupted by a brief failure.

3. Permit the operation of two or more evaporators with the same compressor at various load temperatures.

4. Vary the evaporator pressure in accordance with a fluctuating load that is managed by the load temperature.

Learn more about evaporator pressures visit this link:

brainly.com/app/ask?q=What+is+evaporator+pressures+

#SPJ4

7 0

1 year ago

2. A rock is dropped from rest at the top of a 10 meter tall building. How much time does the rock

ivann1987 [24]

Answer:

1.4 seconds

Explanation:

here u= 0

v= ?

h= 10m

g= 9.8 m/ s*2

using 2as = v^2 - u ^2

2x9.8x10 = v^2 - 0

v^2 = 196

v = 14 m

time = v- u/ a

14 / 98

1.4 seconds

7 0

3 years ago

A 4.5 g coin sliding to the right at 23.8 cm/s makes an elastic head-on collision with a 13.5 g coin that is initially at rest.

Airida [17]

Answer:

a) $v = 11.9\times 10^{-2}\,\frac{m}{s} \,(11.9\,\frac{cm}{s} )$ , b) $\Delta K = 9.559\times 10^{-5}\,J$

Explanation:

a) The final velocity of the 13.5 g coin is found by the Principle of Momentum Conservation:

$(4.5\times 10^{-3}\,kg)\cdot (23.8\times 10^{-2}\,\frac{m}{s} )+(13.5\times 10^{-3}\,kg})\cdot (0\,\frac{m}{s} ) = (4.5\times 10^{-3}\,kg)\cdot (-11.9\times 10^{-2}\,\frac{m}{s} )+(13.5\times 10^{-3}\,kg})\cdot v$

The final velocity is:

$v = 11.9\times 10^{-2}\,\frac{m}{s} \,(11.9\,\frac{cm}{s} )$

b) The change in the kinetic energy of the 13.5 g coin is:

$\Delta K = \frac{1}{2}\cdot (13.5\times 10^{-3}\,kg)\cdot \left[(11.9\times 10^{-2}\,\frac{m}{s} )^{2}-(0\,\frac{m}{s} )^{2}\right]$

$\Delta K = 9.559\times 10^{-5}\,J$

4 0

3 years ago

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