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Degger [83]
4 years ago
5

A cup of hot coffee can be cooled by placing a cold spoon in it. A spoon of which of the following materials would be most effec

tive for this purpose: aluminum, copper, iron, or glass? Assume all spoons have the same mass.
Physics
1 answer:
arsen [322]4 years ago
8 0

Answer: copper

Explanation: when a spoon is placed in a hot coffee, the coffee will cool off based on the concept of heat transfer.

The coffee is at a higher temperature compared to the spoon, hence there is conduction of heat by the spoon from the coffee.

Heat is now transfered from the coffee to the spoon, the rate of heat transfer ( for this case coffee to spoon) is dependent on some properties but for this case, the thermal conductivity is of the most important.

A material of high thermal conductivity have a very fast rate of heat transfer and a material of low thermal conductivity have a slow rate of heat transfer.

Below is the value of thermal conductivity for copper, aluminum, iron and glass.

Copper (385 w/m.K)

Aluminum (205 W/m.K)

Iron (79.5 W/m.K)

Glass (0.8 W/m.K)

It can been seen that copper has the highest value for thermal conductivity which implies that it will conduct heat faster compared to others thus cooling the coffee faster.

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You move a 25 N object 5 meters. If it takes 8 s how much power did you do?
klasskru [66]

Answer:

15.625 watts

Explanation:

Recall that power is defined as the worked performed per unit of time:

Power = Work / time

The work done is Force * distance, so in our case the work is:

Work = 25 M * 5 m = 125 J

Then the power will be:

Power = 125 J / 8 sec = 15.625 watts

6 0
3 years ago
Imagine Two Artificial Satellites Orbiting Earth At The Same Distance. One Satellite Has A Greater Mass Than The Other One? Whic
Bad White [126]

After reading this whole question, I feel like I've already
earned 5 points !

-- Two satellites at the same distance, different masses:

The forces of gravity between two objects are directly
proportional to the product of the objects' masses.  In
other words, the gravitational forces between the Earth
and an object on its surface are proportional to the mass of
the object.  In other words, people with more mass weigh more
on the Earth, and the Earth weighs more on them. 

If the satellites are both at the same distance from Earth,
then the Earth pulls on the one with more mass with greater
force, and also the one with more mass pulls on the Earth
with greater force.

-- Two satellites with the same mass, at different distances:

The forces of gravity between two objects are inversely
proportional to the square of the distance between them. 
In other words, the gravitational forces between the Earth
and an object are inversely proportional to the square of
the distance between the object and the center of the Earth. 

If the satellites both have the same mass, then the Earth
pulls on the nearer one with greater force, and also the
nearer one pulls on the Earth with greater force.

-- Resistor in a circuit when the voltage changes:

The resistance depends on how the resistor was manufactured. 
Its resistance is marked on it, and doesn't change.  It remains
the same whether the voltage changes, the current changes,
the time of day changes, the cost of oil changes, etc.

If you increase the voltage in the circuit where that resistor is
installed, the current through the resistor increases.  If the current
remains constant, then you can be sure that somebody snuck over
to your circuit when you weren't looking, and they either installed
another resistor in series with the original one to make the total
resistance bigger, or else they snipped the original one out of the
circuit and quickly connected one with more resistance in its place.

6 0
3 years ago
A uniform solid sphere has mass m= 7 kg and radius r= 0. 4 m. What is its moment of inertia about an axis tangent to its surface
lilavasa [31]

The moment of inertia of a uniform solid sphere is equal to 0.448 kgm^2.

<u>Given the following data:</u>

Mass of sphere = 7 kg.

Radius of sphere = 0.4 meter.

<h3>How to calculate moment of inertia.</h3>

Mathematically, the moment of inertia of a solid sphere is given by this formula:

I=\frac{2}{5} mr^2

<u>Where:</u>

  • I is the moment of inertia.
  • m is the mass.
  • r is the radius.

Substituting the given parameters into the formula, we have;

I=\frac{2}{5} \times 7 \times 0.4^2\\\\I=2.8 \times 0.16

I = 0.448 kgm^2.

Read more on inertia here: brainly.com/question/3406242

4 0
2 years ago
The atomic mass of an atom do not contain electrons because
Dimas [21]

Answer:

Electrons are so small that it does not affect the mass of atom .

Explanation:

Electrons are much smaller in mass than protons, weighing only 9.11 × 10^-28 grams, or about 1/1800 of an atomic mass unit. Therefore, they do not contribute much to an element's overall atomic mass.

7 0
3 years ago
An object is located 51 millimeters from a diverging lens. The object has a height of 13 millimeters and the image height is 3.5
12345 [234]
You would get 13.7 
mi/51mm=3.5mm/13mm
by solving it you will B13.7mm
3 0
3 years ago
Read 2 more answers
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