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loris [4]
3 years ago
13

A food department is kept at â12°c by a refrigerator in an environment at 30°c. the total heat gain to the food department is

estimated to be 3300 kj/h and the heat rejection in the condenser is 4800 kj/h. determine the power input to the compressor, in kw and the cop of the refrigerator
Physics
1 answer:
slava [35]3 years ago
3 0

As per energy conservation in the reversible engine we can say

Q_2 + W = Q_1

here we know that

Q_2 = 3300 kJ/h

Q_1 = 4800 kJ/h

now from above equation

3300 + W = 4800

W = 1500 kJ/h

now we can convert it into kW

W = 1500\times \frac{kJ}{3600s}

W = 0.42 kW

so above is the power input to the refrigerator

now to find COP we know that

COP = \frac{Q_2}{W}

COP = \frac{3300}{1500} = 2.2

so COP of refrigerator is 2.2

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A stone is thrown horizontally from the top of a tower at the same instant a ball is droppedvertically. Which object is travelin
Igoryamba

The ball is travelling faster when the two objects hits the level ground below.

<h3>Time of motion of the objects</h3>

The time of motion of the objects depends on height and initial velocity of projection of the objects.

The stone has no initial vertical velocity while the ball has initial vertical velocity.

Thus, the ball is travelling faster when the two objects hits the level ground below.

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2 years ago
Why a raw egg shell disolves when submerge in vineger
quester [9]
If you soak this egg shell in vinegar (which is about 4% acetic acid), you start a chemical reaction that dissolves the calcium carbonate shell. The acetic acid reacts with the calcium carbonate in the egg shell and releases carbon dioxide gas that you see as bubbles on the shell.
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3 years ago
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A mortar is like a small cannon that launches shells at steep angles. A mortar crew is positioned near the top of a steep hill.
Elena-2011 [213]

1) Distance down the hill: 1752 ft (534 m)

2) Time of flight of the shell: 12.9 s

3) Final speed: 326.8 ft/s (99.6 m/s)

Explanation:

1)

The motion of the shell is a projectile motion, so we  can analyze separately its vertical motion and its horizontal motion.

The vertical motion of the shell is a uniformly accelerated motion, so the vertical position is given by the following equation:

y=(u sin \theta)t-\frac{1}{2}gt^2 (1)

where:

u sin \theta is the initial vertical velocity of the shell, with u=156 ft/s and \theta=49.0^{\circ}

g=32 ft/s^2 is the acceleration of gravity

At the same time, the horizontal motion of the shell is a uniform motion, so the horizontal position of the shell at time t is given by the equation

x=(ucos \theta)t

where u cos \theta is the initial horizontal velocity of the shell.

We can re-write this last equation as

t=\frac{x}{u cos \theta} (1b)

And substituting into (1),

y=xtan\theta -\frac{1}{2}gt^2 (2)

where we have choosen the top of the hill (starting position of the shell) as origin (0,0).

We also know that the hill goes down with a slope of \alpha=-41.0^{\circ} from the horizontal, so we can write the position (x,y) of the hill as

y=x tan \alpha (3)

Therefore, the shell hits the slope of the hill when they have same x and y coordinates, so when (2)=(3):

xtan\alpha = xtan \theta - \frac{1}{2}gt^2

Substituting (1b) into this equation,

xtan \alpha = x tan \theta - \frac{1}{2}g(\frac{x}{ucos \theta})^2\\x (tan \theta - tan \alpha)-\frac{g}{2u^2 cos^2 \theta} x^2=0\\x(tan \theta - tan \alpha-\frac{gx}{2u^2 cos^2 \theta})=0

Which has 2 solutions:

x = 0 (origin)

and

tan \theta - tan \alpha=\frac{gx}{2u^2 cos^2 \theta}=0\\x=(tan \theta - tan \alpha) \frac{2u^2 cos^2\theta}{g}=1322 ft

So, the distance d down the hill at which the shell strikes the hill is

d=\frac{x}{cos \alpha}=\frac{1322}{cos(-41.0^{\circ})}=1752 ft=534 m

2)

In order to find how long the mortar shell remain in the air, we can use the equation:

t=\frac{x}{u cos \theta}

where:

x = 1322 ft is the final position of the shell when it strikes the hill

u=156 ft/s is the initial velocity of the shell

\theta=49.0^{\circ} is the angle of projection of the shell

Substituting these values into the equation, we find the time of flight of the shell:

t=\frac{1322}{(156)(cos 49^{\circ})}=12.9 s

3)

In order to find the final speed of the shell, we have to compute its horizontal and vertical velocity first.

The horizontal component of the velocity is constant and it is

v_x = u cos \theta =(156)(cos 49^{\circ})=102.3 ft/s

Instead, the vertical component of the velocity is given by

v_y=usin \theta -gt

And substituting at t = 12.9 s (time at which the shell strikes the hill),

v_y=(156)(cos 49^{\circ})-(32)(12.9)=-310.4ft/s

Therefore, the  final speed of the shell is:

v=\sqrt{v_x^2+v_y^2}=\sqrt{(102.3)^2+(-310.4)^2}=326.8 ft/s=99.6 m/s

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3 years ago
a machine gun fires 10 rounds per second the speed of the bullets is 300 m/s. what is the distance in the air between the flying
vovangra [49]
<span>(300 m/s)/(10 r/s) = 30 m/round.</span>
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3 years ago
How do you calculate the mass of an object accelerating at22.35m/s2 with a force of 120N
Arte-miy333 [17]

Answer:

The mass of object is calculated as 5.36 kg

Explanation:

The known terms to find the mass are:

           acceleration of object (a) = 22.35 m/s^{2}

                        Force exerted (F) = 120N

                        mass of an object (m) = ?

From Newton's second law of motion;

                                   F = ma

                           or, 120 = m × 22.35

                          or, m= \frac{120}{22.35} kg

                           ∴ m = 5.36 kg

3 0
2 years ago
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