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3 years ago

A water heater warms 35 l of water from a temperature of 22.7 c to a temperature of 83.7

1 answer:

8 0

The amount of energy needed to increase the temperature of a substance by $\Delta T$ is given by
$Q=m C_s \Delta T$
where
m is the mass of the substance
$C_s$ is its specific heat capacity
$\Delta T$ is the increase in temperature

The water volume is $V=35 L= 35 dm^3 = 0.035 m^3$ , since its density is $d=1000 kg/m^3$ , the mass of this sample of water is
$m=dV=(1000 kg/m^3)(0.035 m^3)=35 kg$

The water specific heat capacity is $C_s = 4.18 kJ/kg ^{\circ}C$

and the increase in temperature is $\Delta T=83.7 ^{\circ}C-22.7 ^{\circ}C=61^{\circ}C$

Therefore, the amount of energy needed is
$Q=mC_s \Delta T=(35 kg)(4.18 kJ/kg ^{\circ}C)(61^{\circ}C)=8924 kJ = 8.92 \cdot 10^6 J$

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49. \ A rectangular plate is rotating with a constant angular speed about an axis that passes perpendicularly through one corner

faust18 [17]

Answer:

$\frac{L_1}{L_2} = \sqrt{(n^2 - 1)}$

Explanation:

For this interesting problem, we use the definition of centripetal acceleration

a = v² / r

angular and linear velocity are related

v = w r

we substitute

a = w² r

the rectangular body rotates at an angular velocity w

We locate the points, unfortunately the diagram is not shown. In this case we have the axis of rotation in a corner, called O, in one of the adjacent corners we call it A and the opposite corner A

the distance OB = L₂

the distance AB = L₁

the sides of the rectangle

It is indicated that the acceleration in in A and B are related

$a_A = n \ a_B$

we substitute the value of the acceleration

w² r_A = n r_B

the distance from the each corner is

r_B = L₂

r_A = $\sqrt{L_1^2 + L_2^2}$

we substitute

\sqrt{L_1^2 + L_2^2} = n L₂

L₁² + L₂² = n² L₂²

L₁² = (n²-1) L₂²

4 0

3 years ago

Suppose a scoentist was able to construct a barometer with a liquid being denser than mercury , then how high would the liquid r

ki77a [65]

Answer:

the liquid has less height than the mercury

h_{ liquid} = $\frac{\rho_{Hg} }{\rho_{liqid}} \ h_{Hg}$

Explanation:

The pressure as a function of the height is given by

P = ρ g h

where ρ is the density of the liquid, g the acceleration of gravity and h the height reached by the column of the liquid

In that case they say that the pressure is the standard one that is P = 1.01 10⁵ Pa = 760 mmHg

The first way to give the pressure is in SI units and the second way is the height that the mercury column reaches

In the case of building a barometer with a liquid that has a density greater than that of mercury

ρ_liquid > ρ_Hg

the pressure

P =ρ_lquid g h_liquid

if we have the same pressure

ρ_{Hg} g h_{Hg} = ρ_{liquid} g h_{liquid}

h_{ liquid} = $\frac{\rho_{Hg} }{\rho_{liqid}} \ h_{Hg}$

therefore the liquid has less height than the mercury

7 0

3 years ago

what can you say about the motion of an object if its speed time graph is a straight line parallel to the time axis ? Also draw

MaRussiya [10]

Answer:

It says about the motion and the graph of the object is stationary, basically travelling at the same speed at any time of the graph. It will never change.

Explanation:

To draw a diagram:

1. Draw an object and represent the speed as stationary and constant at any time.

5 0

2 years ago

A boat traveling across a river has a resultant velocity of 10 km/h and travels 34 degrees with respect to the shore. A) What is

vodka [1.7K]

Answer:

a) 1.55 m/s

b) 2.3 m/s

Explanation:

We know that the boat travels across the river, if we define the river as the x-axis, then the velocity of the boat is only on the y-axis.

Then we can write the velocity of the boat in still water as:

S = (0, B)

Now, when the boat is on the river, the velocity of the boat will be equal to the velocity of the boat in still water plus the velocity of the river.

The velocity of the river is:

v = (R, 0).

Then the velocity of the boat in that river is:

V' = (0, B) + (R, 0) = (R, B)

Now, we know that the velocity of the boat is 10km/h, and it travels at an angle of 34° with respect to the shore.

We can use the Pythagoreans theorem to write the components of this velocity as:

x-axis component = 10km/h*cos(34°) = 8.29 km/h

y-axis component = 10km/h*sin(34°) = 5.59 km/h

Then the velocity of the boat can be written in components as:

velocity = ( 8.29 km/h, 5.59 km/h)

And we knew that the velocity of the boat was written as (R, B)

Then we must have:

R = 8.29 km/h

B = 5.59 km/h

a) The speed of the boat in m/s:

We know that the speed of the boat is 5.59 km/h.

First, we know that:

1km = 1000m, then:

5.59 km/h = 5.59*(1000m)h = 5,590 m/h

And we know that:

1h = 3600s

Then we can write:

5,590 m/h = 5,590 m/(3600s) = 1.55 m/s

b) The speed of the river in m/s:

We know that the speed of the river is 8.29 km/h

Using the same reasoning as above, we can do the change of units as follows:

8.29 km/h = 8.29 (1000m)/(3600s) = 2.3 m/s

6 0

3 years ago

What are the functions of the female reproductive system?

gulaghasi [49]

The female reproductive system is designed to carry out several functions. It produces the female egg cells necessary for reproduction, called the ova or oocytes. The system is designed to transport the ova to the site of fertilization.

7 0

3 years ago