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N76 [4]
3 years ago
8

Which material is the best heat insulator? metal wood plastic glass

Physics
2 answers:
LuckyWell [14K]3 years ago
6 0

Answer:

Wood

Explanation:

The measure of any material to conduct heat is called its thermal conductivity. The thermal conductivity of metal is very high as compared to insulators and semiconductors.

The thermal conductivity of wood is 0.12-0.04 W/m K. Plastics have thermal conductivity of 0.2 W/m K. The thermal conductivity of fiber glass or foam glass is 0.045 W/m K

Wood is a best heat insulator. This is because, the atoms of wood have much tightly bound electrons.              

Hence, the correct option is (b).                    

OlgaM077 [116]3 years ago
5 0
Of the materials listed wood is the best insulator. It would be the least hot if exposed to similar temperatures.
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A gas exerts less pressure when it has a
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3 years ago
A low resistance light bulb and a high resistance light bulb are connected in parallel with each other. Which bulb is brighter i
sweet [91]
<h2>Answer:</h2>

The bulb with low resistance will be brighter.

<h2>Explanation:</h2>

The brightness of a bulb is a function of both the voltage across the bulb and current flowing through the bulb. The higher the voltage, the higher the current. Hence the brighter the bulb.

Now, according to the question, the bulbs (the high resistance bulb and the low resistance bulb) are connected in parallel with each other. This means that the same voltage passes across them.

Also, we know that according to Ohm's law, the voltage (V) and current (I) through a conductor are related by the following equation;

V =  I x R                -------------------(i)

Where;

R is the resistance of the conductor.

We can re-write equation (i) as follows;

I = V / R               -----------------------(ii)

According to equation (ii), at fixed voltage (V), the current (I) will increase as the resistance (R) decreases.

Now, since the two bulbs have the same voltage, the bulb with the low resistance will allow a larger flow of current than the bulb with high resistance.  Therefore, as said earlier that brightness is dependent on voltage and current, the bulb with the low resistance (and having larger current at some voltage) will be brighter than the bulb with the high resistance (having smaller current at same voltage).

6 0
4 years ago
A ball is dropped from a building taking 3sec to fall to the ground. Calculate:
GenaCL600 [577]

Answer:

Vf = 29.4 m/s

h = 44.1 m

Explanation:

Data:

  • Initial Velocity (Vo) = 0 m/s
  • Gravity (g) = 9.8 m/s²
  • Time (t) = 3 s
  • Final Velocity (Vf) = ?
  • Height (h) = ?

==================================================================

Final Velocity

Use formula:

  • Vf = g * t

Replace:

  • Vf = 9.8 m/s² * 3s

Multiply:

  • Vf = 29.4 m/s

==================================================================

Height

Use formula:

  • \boxed{h=\frac{g*(t)^{2}}{2}}

Replace:

  • \boxed{h=\frac{9.8\frac{m}{s^{2}}*(3s)^{2}}{2}}

Multiply time squared:

  • \boxed{h=\frac{9.8\frac{m}{s^{2}}*9s^{2}}{2}}

Simplify the s², and multiply in the numerator:

  • \boxed{h=\frac{88.2m}{2}}

It divides:

  • \boxed{h=44.1\ m}

What is the velocity when falling to the ground?

The final velocity is <u>29.4 meters per seconds.</u>

How high is the building?

The height of the building is <u>44.1 meters.</u>

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What kind of rock is this?
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The picture is kinda blurry but it looks like granite which is metamorphic.
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