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dem82 [27]
3 years ago
10

You pour 250 g of tea into a Styrofoam cup, initially at 80∘C and stir in a little sugar using a 100-g aluminum 20∘C spoon and l

eave the spoon in the cup. Assume the specific heat of tea is 4180 J/kg⋅∘C and the specific heat of aluminum is 900 J/kg⋅∘C. Part APart complete What is the highest possible temperature of the spoon when you finally take it out of the cup?
Physics
1 answer:
jok3333 [9.3K]3 years ago
3 0

To solve this problem it is necessary to apply the concepts related to the conservation of energy and heat transferred in a body.

By definition we know that the heat lost must be equal to the heat gained, ie

Q_g = Q_l

Where,

Q = Heat exchange

The heat exchange is defined as

Q = c_p m \Delta T

Where,

c_p = Specific heat

m = mass

\Delta T= Change in Temperature

Therefore replacing we have that

Q_g = Q_l

c_{p-tea} m \Delta T =  c_{p-al} m \Delta T

Replacing with our values we have that

0.25*4180*(80-T) = 0.1*900*(T-20)

11.61*(80-T) = T-20

T= \frac{948.8}{11.61}

T = 75.24\°C

Therefore the highest possible temperature of the spoon when you finally take it out of the cup is 75.24°C

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The spectra of most stars are dark-line spectra because ________.
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Because dark line spectra result from passing white light through ionized gasses and plasmas, which is what the atmosphere of stars are made of.  These frequencies are scattered by the star's atmosphere as it leaves the surface (photosphere) of the star, and don't make it to earth.
5 0
3 years ago
7. Two people are pushing a 40.0kg table across the floor. Person 1 pushes with a force of 490N
artcher [175]

Answer:

20.4 m/s^{2}

Explanation:

To start doing this problem, first draw a free body diagram of the table. My teacher always tells us to do this, and I find that it is very helpful. I have attached a free body diagram to this answer- take a look at it.

First, let us see if Net force = MA. To do that, we need to determine whether the object is at equilibrium horizontally. For an object to be at equilibrium, it either needs to be moving at a constant velocity or not moving at all. Also, if an object is at equilibrium, there will not be any acceleration. But we know that there IS acceleration horizontally, so it cannot be in equilibrium. If it is not in equilibrium, we can use the formula ∑F= ma.

Let us determine the net force. Since the object is moving horizontally, we can ignore the weight and normal force, because they are vertical forces. The only horizontal forces we need to worry about are the applied force and force of friction.

Applied force = 1055 N (490 + 565)

Friction force= Unknown

To find the friction force, use the kinetic friction formula, Friction = μkN

μk is the coefficient, which the problem includes- it is 0.613.

N is the normal force, which we have to find.

*To find the normal force, we have to determine if the object is at equilibrium VERTICALLY. Since it has no acceleration vertically (it's not moving up/down), it is at equilibrium. Now, when an object is at equilibrium in one direction, it means that all the forces in that direction are equal. What are our vertical forces? Weight (mg) and Normal force (N). So it means that the Normal force is equal to the Weight.

Weight = mg = (40)(9.8) = 392 N

Normal force = 392 N

Now, plug it back into the formula (μkN): (0.613)(392) = 240.296 N

Friction = 240.296 N

Now that we know the friction, we can find the horizontal net force. Just subtract the friction force, 240.296 from the applied force, 1055 N

Horizontal Net Force: 814.704 N

Now that we know the net force, plug in the numbers for the formula

∑F= ma.

814.704 = (40.0)(a)

*Divide on both sides)

a = 20.3676 m/s^2

Round it to 3 significant figures, to get:

20.4 m/s^{2}

7 0
3 years ago
Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is mo
kkurt [141]

Answer:increased

Explanation:

It is given that elevator speed is increasing while moving upward i.e.its acceleration is increasing .

This causes the apparent to be increased if measured using weighing machine.

considering upward direction to be positive

N-mg=ma

N=m(g+a)

where N=Normal reaction=Apparent weight

a=acceleration of Elevator

thus you feel as if your weight is increased.

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Which of the following is not a reason fluorescent lamps are advantages over incandescent lamps?
iren2701 [21]

It’s because flourecent lights operate at higher temperatures than incadecent lights.

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What is the average of the speed of light
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The average speed of light is 186,000 mph
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