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3 years ago

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A heat pump receives heat from a lake that has an average winter time temperature of 6o C and supplies heat into a house having

an average temperature of 25o C. (a) If the house loses heat to the atmosphere at the rate of 60,000 kJ/h, determine the minimum power supplied to the heat pump (in kW) that can maintain the interior temperature of the house at 25o C. (b) Suppose the heat pump absorbs energy from the ground (10o C) instead of the lake, Calculate the minimum power (in kW) required for the heat pump.

1 answer:

Natalija [7]3 years ago

4 0

Answer:

Explanation:

60000 kJ / h = 60000 x 1000 / (60 x 60 )

= 16667 J /s

a)

$\frac{Q_H}{W} =\frac{T_H}{T_H-T_C}$

where $Q_H$ and $W$ are heat supplied and heat given from outside source .

Here $Q_H$ = 16667 J/s

$\frac{T_H}{T_H-T_C}=\frac{298}{298-279}$

= 15.684

$Q_H = 16667 J/s$

16667 / W = 15.684

W= minimum power supplied = 1062.7 W.

b )

If $T_C=283K$

$\frac{T_H}{T_H-T_C}=\frac{298}{298-283}$

=19.87

$\frac{Q_H}{W} = 19.87$

$W=\frac{Q_H}{19.87}$

$W=\frac{16667}{19.87}$

= 838.8 W .

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What is the resultant force of the free body diagram?

GaryK [48]

1) Magnitude of the net force: 20.8 N

2) Angle: $35.2^{\circ}$ clockwise from positive x-direction

Explanation:

1)

First of all, we need to find the components of the resultant force along the horizontal and vertical direction.

We observe that there are two forces acting along the horizontal direction:

$F_1=33 N\\F_2 = 16 N$

We notice that they act in opposite directions, so the net force in the horizontal direction is the difference between these two forces:

$F_x =F_1-F_2=33-16=17 N$ (to the right)

Instead, there is only one force acting in the vertical direction, so the net force in the vertical direction is:

$F_y=F_3=12 N$ (downward)

Therefore, the magnitude of the net force can be found by using Pythagorean's theorem:

$F=\sqrt{F_x^2+F_y^2}=\sqrt{17^2+12^2}=20.8 N$

2)

Now we have to find the angle of the resultant net force. We can do it by using the following equation:

$tan \theta = \frac{F_y}{F_x}$

where

$\theta$ is the angle, measured as clockwise from the positive x-direction (because the vertical net force is downward)

$F_y = 12 N$ is the vertical net force

$F_x=17 N$ is the horizontal net force

Solving, we find:

$tan \theta=\frac{12}{17}=0.706$

And so the angle is

$\theta=tan^{-1}(0.706)=35.2^{\circ}$

In a direction down with respect to the right.

Learn more about forces:

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3 years ago

Two long, parallel wires are separated by a distance of 2.00 cm . The force per unit length that each wire exerts on the other i

RUDIKE [14]

Answer:

a) current in the second wire is 5.60A

b) opposite directions

Explanation:

a) We need to find the current of wire, the magnitude of the force per unit length between the two wires carrying current I and I¹ is given by

$\frac{F}{L} = \frac{U_0I^1}{2\pi r} \\\\I^1 = \frac{F2\pi r}{LU_0I}$

$= (3.6 * 10^-^5)\frac{2\pi (0.02)}{4\pi * 10^-^7)(0.64)} \\= 5.60A$

b) knowing that for a two parallel conductor carrying current in the same direction attracts each other, and for a two parallel conductors carrying carying current in opposite direction repels eachother.

therefore, since the two wire repel each other then the current in the second wire must flow in the opposite direction of the current in the first wire.

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4 years ago

Which type of stress causes deformation that leads to earthquakes at converging plate boundaries?

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3 years ago

what is the energy (in eV units) carried by one photon violet light that has a wavelength of 4.5e-7?

DaniilM [7]

The energy of a photon is given by
$E=hf$
where h is the Planck constant and f is the photon frequency.

We can find the photon's frequency by using the following relationship:
$f= \frac{c}{\lambda}$
where c is the speed of light and $\lambda$ is the photon's wavelength. By plugging numbers into the equation, we find
$f= \frac{c}{\lambda}= \frac{3 \cdot 10^8 m/s}{4.5 \cdot 10^{-7} m}=6.67 \cdot 10^{14}Hz$

And so now we can find the photon energy
$E=hf=(6.6 \cdot 10^{-34} Js)(6.67 \cdot 10^{14}Hz )=4.4 \cdot 10^{-19} J$

We know that 1 Joule corresponds to
$1 J = 1.6 \cdot 10^{-19} eV$
So we can convert the photon's energy into electronvolts:
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4 years ago

A ball of mass m= 450.0 g traveling at a speed of 8.00 m/s impacts a vertical wall at an angle of θi =45.00 below the horizontal

Mkey [24]

Answer:

F = 20.4 i ^

Explanation:

This exercise can be solved using the ratio of momentum and amount of movement.

I = F t = Dp

Since force and amount of movement are vector quantities, each axis must be worked separately.

X axis

Let's look for speed

cos 45 = vₓ / v

vₓ = v cos 45

vₓ = 8 cos 45

vₓ = 5,657 m / s

We write the moment

Before the crash p₀ = m vₓ

After the shock $p_{f}$ = -m vₓ

The variation of the moment Δp = mvₓ - (-mvₓ) = 2 m vₓ

The impulse on the x axis Fₓ t = Δp

Fₓ = 2 m vₓ / t

Fx = 2 0.450 5.657 / 0.250

Fx = 20.4 N

We perform the same calculation on the y axis

sin 45 = vy / v

vy = v sin 45

vy = 8 sin 45

vy = 5,657 m / s

We calculate the initial momentum po = m $v_{y}$

Final moment $p_{f}$ = m $v_{y}$

Variations moment Δp = m $v_{y}$ - m $v_{y}$ = 0

Force in the Y-axis $F_{y}$ = 0

Therefore the total force is

F = fx i ^ + Fyj ^

F = Fx i ^

F = 20.4 i ^

3 0

3 years ago