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blagie [28]
3 years ago
10

În ce raport de mase trebuie amestecate două cantități din același lichid, având temperaturile t1=10 grade Celsius, respectiv t2

=65 grade Celsius, pentru a obține o temperatură de echilibru t=45 grade Celsius?
Physics
1 answer:
Brilliant_brown [7]3 years ago
8 0

Răspuns:

7: 4

Explicaţie:

Formula pentru calcularea cantității de căldură absorbită este exprimată ca;

Q = mc∆t

m este masa substanței

c este capacitatea termică specifică

∆t este schimbarea temperaturii

Conform legii calorimetriei, căldura pierdută de substanța rece = căldura câștigată de substanța fierbinte.

Folosind formula

(mc∆t) rece = (mc∆t) fierbinte

McCw∆tc = MhCw∆th

Deoarece au aceeași capacitate de căldură specifică, se vor anula. Ecuația devine;

Mc∆tc = Mh∆th ...... 1

Pentru apa rece;

∆tc = 45 ° C - 10 ° C

∆tc = 35 ° C

Pentru apa fierbinte:

∆th = 65 ° C - 45 ° C

∆th = 20 ° C

Înlocuiți în ecuația 1;

Mc (35) = Mh (20)

35Mc = 20Mh

Luând raportul dintre masa apei reci și cea fierbinte:

Mh / Mc = 35/20

Mh / Mc = 7/4

Prin urmare, lichidul trebuie amestecat împreună în raportul 7: 4

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Answer:

Friction

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As the toy cars rolls away, more friction is created. The more friction there is, the more friction on surface rubs against another which creates friction which in-term slows it down. Hope this helps.

4 0
2 years ago
The kinetic friction force between a 60.0-kg object and a horizontal surface is 50.0 N. If the initial speed of the object is 25
Vikki [24]

Answer:

375 m.

Explanation:

From the question,

Work done by the frictional force = Kinetic energy of the object

F×d = 1/2m(v²-u²)..................... Equation 1

Where F = Force of friction, d = distance it slide before coming to rest, m = mass of the object, u = initial speed of the object, v = final speed of the object.

Make d the subject of the equation.

d = 1/2m(v²-u²)/F.................. Equation 2

Given: m = 60.0 kg, v = 0 m/s(coming to rest), u = 25 m/s, F = -50 N.

Note: If is negative because it tends to oppose the motion of the object.

Substitute into equation 2

d = 1/2(60)(0²-25²)/-50

d = 30(-625)/-50

d = -18750/-50

d = 375 m.

Hence the it will slide before coming to rest = 375 m

6 0
3 years ago
An aquarium open at the top has 30-cm-deep water in it. You shine a laser pointer into the top opening so it is incident on the
Setler [38]

Answer:

You must add 8cm of water to the tank

Explanation:

In order to find how much the height is we will use the Snell Refraction law

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This law relates the index of refraction of the water (n2), the index of refraction of the air (n1), the incidence angle relative to the vertical (theta1) and the refraction angle relative to the vertical (theta2) by using the next equation:

(n1)*(sin(theta1))=(n2)*(sin(theta2))

Then we will find the refraction angle relative to the vertical this way:

(n1/n2)*(sin(theta1))=sin(theta2)

(1/1.33)*(sin(45))=sin(theta2)

Then, theta2=32.12°

Now that we have this information we can imagine a triangle with a 30cm height and a 32.12° angle. This way we can find how much X is, this X will be the distance between the vertical line and the spot the beam hits the bottom, so we can use some trigonometry to find it, this way:

tan(32.12)=(X/30cm)

X=(tan(32.12))*(30cm)

Then, X=18.8cm, we can approximate it to 19cm

Once we have X we will add 5cm to it which is how much the beam needs to be moved, then the new X will be 24cm

Now, with the new horizontal distance we will find the new vertical distance, let´s call it Y, this way we will know how much water we must add to move the beam, then we will have a triangle with a vertical distance called Y, the same 32.12° angle will be used as we are still working with the air-water interface and a 19cm horizontal distance, then:

tan(32.12)=(24cm/Y)

Y=(24cm/tan(32.12))

Then, Y=38cm

In this case, you must add 8cm of water to the tank to move the beam on the bottom 5cm

5 0
3 years ago
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lapo4ka [179]

Answer:

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Maksim231197 [3]

Answer:

8%

Explanation:

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