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Burka [1]
3 years ago
7

A student drops two metallic objects into a 120-g steel container holding 150 g of water at 25°C. One object is a 206-g cube of

copper that is initially at 88°C, and the other is a chunk of aluminum that is initially at 5.0°C. To the surprise of the student, the water reaches a final temperature of 25°C, precisely where it started. What is the mass of the aluminum chunk?
Physics
1 answer:
spayn [35]3 years ago
3 0

Answer:

Mass of the aluminium chunk = 278.51 g

Explanation:

For an isolated system as given the energy lost and gains in the system will be zero therefore sum of all transfer of energy will be zero,as the temperature will also remain same

A specific heat formula is given as                  

Energy Change = Mass of liquid x Specific Heat Capacity x Change in temperature

                                       Q =  m×c×ΔT

                        Heat gain by aluminium + heat lost by copper  = 0    (1)

For Aluminium:

      Q = m\times0.897\frac{J}{g.k}\times(25-5)

      Q = m x 17.94 joule

For Copper:

Q= 206g\times0.385\frac{J}{g.k} \times(88-25)

       Q= 4996.53 Joule

from eq 1

     m x 17.94 = 4996.53

     mass of aluminium = \frac{4996.53}{17.94} g

    Mass of the aluminium chunk = 278.51 g

                         

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As it is given that stone is spherical in shape so first we will find its volume

V = \frac{4}{3}\pi r^3

V = \frac{4}{3}\pi *(\frac{0.06}{2})^3

V = 1.13 * 10^{-4} m^3

Now it is given that it's specific gravity is 10.8

So density of rock is

\rho = 10.8 * 10^3 kg/m^3

mass of the stone will be

m = \rho V

m = 10.8* 10^3 * 1.13 * 10^{-4}

m = 1.22 kg

now change in potential energy is given as

\Delta U = mgH

here

g = gravity on planet = 0.278 m/s^2

H = height lifted upwards = 15 cm

\Delta U = 1.22* 0.278 * 0.15

\Delta U = 0.051 J

Now energy supplied by internal circuit of robot is given by

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V = voltage supplied = 10 V

i = current = 1.83 mA

t = time = 12 s

E = 10* 1.83 * 10^{-3} * 12

E = 0.22 J

Now efficiency is defined as the ratio of output work with given amount of energy used

\eta = \frac{\Delta U}{E}*100

\eta = \frac{0.051}{0.22} = 0.23

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5 0
3 years ago
Suppose you are standing at the exact center of a park surrounded by a circular road. An ambulance drives completely around this
vladimir2022 [97]

Answer: The pitch of the sound does not change.

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Doppler effect is a mathematical equation that gives the relationship between the observed frequency by an observer from any sound source and the relative motion between the observer and the source.

Mathematically,

f'= (v+v') /(v-vs) * f

Where f' = observed frequency of sound wave

v= speed of sound in air

v'= velocity of observer relative to sound source

vs= velocity of sound source relating to observer

f= frequency of sound produced by source

The observer is at the center, thus the distance between the observer and the source is constant (according to mensuration, the radius is constant for any given circle and since the car is moving along a circular path and the observer is at the center, thus the distance between them is constant), thus making the relative velocity between the observer and the source constant (vs=constant).

Also the frequency of sound wave produce by the source is a constant (f=constant)

The speed of sound in air is also a constant (v=336m/s)

The observer is standing at the center thus he is not moving, hence the relative motion between observer and source is also constant (v'=constant)

Since all parameters are constant, then the observed frequency will be constant too.



4 0
3 years ago
Two cars leave towns 680 kilometers apart at the same time and travel toward each other. one car's rate is 10 kilometers per hou
Evgen [1.6K]

D = distance between the cars at the start of time = 680 km

v₁ = speed of one car

v₂ = speed of other car = v₁ - 10

t = time taken to meet = 4 h

distance traveled by one car in time "t" + distance traveled by other car in time "t" = D

v₁ t + v₂ t = D

(v₁ + v₂) t = D

inserting the values

(v₁ + v₁ - 10) (4) = 680

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rate of slower car is given as

v₂ = v₁ - 10

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5 0
3 years ago
A beam of white light enters a prism of crown glass (n = 1.5) from air (n = 1.00). Once inside, the colors in the light disperse
eduard

Answer:

= 2.33

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.According to snell's law:

n1sin i = n2sin r ,

where n1 is refractive index of the medium in which incident ray is travelling, n2 is the refractive index of the medium in which refracted ray is travelling,

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Given that,

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7 0
3 years ago
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Answer:

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but:
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The velocity is negative, because the object is thrown downwards
7 0
2 years ago
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