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3 years ago

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A 20 watt light bulb is left burning inside a refrigerator operating on a reverse Carnot cycle. If the refrigerator also draws 2

0 watts of electrical power to operate its condenser, can it cool its interior below room temperature while the bulb is on? Explain why or why not

1 answer:

Gwar [14]3 years ago

8 0

Explanation:

Given that,

Power drawn by the refrigerator = 20 watt

Power of burning light inside = 20 watt

Room temperature = 27°C

We need to calculate the temperature

Using formula of coefficient of refrigerator

$COR_{R}=\dfrac{Q_{c}}{W}$

$\dfrac{Q_{c}}{W}=\dfrac{T_{c}}{T_{H}-T_{c}}$

Put the value into the formula

$\dfrac{20}{20}=\dfrac{T_{c}}{T_{H}-T_{c}}$

$\dfrac{T_{c}}{T_{H}-T_{c}}=1$

$T_{h}=2T_{c}$

$T_{c}=\dfrac{T_{h}}{2}$

$T_{c}=\dfrac{27+273}{2}$

$T_{c}=150\ K$

$T_{c}$ is less than $T_{h}$

Therefore, refrigerator cools its interior below room temperature while the bulb is on.

Hence, This is the required solution.

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On a straight road, a car speeds up at a constant rate from rest to 20 m/s over a 5 second interval and a truck slows at a const

IceJOKER [234]

Answer:

a)

Explanation:

Since the car speeds up at a constant rate, we can use the kinematic equation for distance (assuming that the initial position is x=0, and choosing t₀ =0), as follows:

$x_{fc} = v_{o}*t + \frac{1}{2}*a*t^{2} (1)$

Since the car starts from rest, v₀ =0.
We know the value of t = 5 sec., but we need to find the value of a.
Applying the definition of acceleration, as the rate of change of velocity with respect to time, and remembering that v₀ = 0 and t₀ =0, we can solve for a, as follows:

$a_{c} =\frac{v_{fc}}{t} = \frac{20m/s}{5s} = 4 m/s2 (2)$

Replacing a and t in (1):

$x_{fc} = v_{o}*t + \frac{1}{2}*a*t^{2} = \frac{1}{2}*a*t^{2} = \frac{1}{2}* 4 m/s2*(5s)^{2} = 50.0 m. (3)$

Now, if the truck slows down at a constant rate also, we can use (1) again, noting that v₀ is not equal to zero anymore.
Since we have the values of vf (it's zero because the truck stops), v₀, and t, we can find the new value of a, as follows:

$a_{t} =\frac{-v_{to}}{t} = \frac{-20m/s}{10s} = -2 m/s2 (4)$

Replacing v₀, at and t in (1), we have:

$x_{ft} = 20m/s*10.0s + \frac{1}{2}*(-2 m/s2)*(10.0s)^{2} = 200m -100m = 100.0m (5)$

Therefore, as the truck travels twice as far as the car, the right answer is a).

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2 years ago

What is the tangential velocity of a record player which makes 11 revolutions in 20 seconds? Please help

Deffense [45]

Answer:

oh umm it think its TV=11x*20s

Explanation:

4 0

2 years ago

A car accelerates in the +x direction from rest with a constant acceleration of a1 = 1.76 m/s2 for t1 = 20 s. At that point the

alex41 [277]

Answer:

(a) $v_1 = a_1t_1 = 1.76 t_1$

(b) It won't hit

(c) 110 m

Explanation:

(a) the car velocity is the initial velocity (at rest so 0) plus product of acceleration and time t1

$v_1 = v_0 + a_1t_1 = 0 +1.76t_1 = 1.76t_1$

(b) The velocity of the car before the driver begins braking is

$v_1 = 1.76*20 = 35.2m/s$

The driver brakes hard and come to rest for t2 = 5s. This means the deceleration of the driver during braking process is

$a_2 = \frac{\Delta v_2}{\Delta t_2} = \frac{v_2 - v_1}{t_2} = \frac{0 - 35.2}{5} = -7.04 m/s^2$

We can use the following equation of motion to calculate how far the car has travel since braking to stop

$s_2 = v_1t_2 + a_2t_2^2/2$

$s_2 = 35.2*5 - 7.04*5^2/2 = 88 m$

Also the distance from start to where the driver starts braking is

$s_1 = a_1t_1^2/2 = 1.76*20^2/2 = 352$

So the total distance from rest to stop is 352 + 88 = 440 m < 550 m so the car won't hit the limb

(c) The distance from the limb to where the car stops is 550 - 440 = 110 m

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3 years ago

To find the specific heat capacity of a solid of mass 600 g whose temperature was 40oC, it was placed in a calorimeter that cont

RSB [31]

Explanation:

The specific heat capacity is the heat or energy required to change one unit mass of a substance of a constant volume by 1 °C. The formula is Cv = Q / (ΔT ⨉ m) .

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3 years ago

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A 45 kg object has a momentum of 225 kg-m/s northward. What is the object's velocity?

melomori [17]

Answer: 5 m/s North

Explanation:

Velocity = Momentum/Mass

Velocity = 225 kg*m/s/45kg

Velocity = 5 m/s North

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2 years ago