PHYSICS HIGH SCHOOL

How much heat energy (in megajoules) is needed to convert 7 kilograms of ice at –9°C to water at 0°C?A. 2.48 MJ
B. 2.13 MJ
C. 3.26 MJ
D. 3.09 MJ

Answers

Answer 1
Answer:

Answer;

A. 2.48 MJ

Explanation;

-Heat energy may be given by the product of specific heat capacity , mass and change in temperature, or the product of heat capacity and change in temperature.

-When a substance is changing from solid state to liquid state then the heat energy is calculate by multiplying the latent heat of fusion of a substance by the mass. Latent heat of fusion of ice =3.34×10⁵J/kg and specific heat capacity of water is 2100 J/kg/K.

Specific heat energy: Q = mcΔT

Latent heat energy: Q = mLf

In this case the heat energy required will be;

Heat required to melt ice and raise its temperature to 0°C:

Q₁ = mLf+mciΔT

Q₁ = (7 kg*3.34×10⁵J/kg) + ((7kg*2100J/kgK*{0°C-(9°C)})

= 2.48 MJ (MEGA JOULES)
Answer 2
Answer:

1.       Energy released from changing the phase of a substance from the liquid phase to solid phase can be calculated by using the specific latent heat of fusion. The heat of fusion of water at 0 degrees Celsius is 334 J/g. Calculation are as follows:

 

 Energy = 7000 grams x 334 J/g

 Energy = 2338000 J or 2.38 MJ

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Which of the following most directly shows how physics affects society?A. A car comes equipped with side air bags.
B. A business conducts meetings over the Internet.
O C. A surgeon performs a heart transplant.
D. A singer wins an award for a song she wrote.

Answers

the answer is definitely A.

An object is dropped from a height H above the ground. This free-falling object requires 1.02 s to travel the last 39 m before hitting the ground. From what height H above the ground did the object fall?

Answers

Answer:

H = 95.3 m

Explanation:

Let the height from which object fall down is H

so the total time to fall is given as

H = (1)/(2)gt^2

now it cover 39 m in last 1.02 s of its path

H - 39 = (1)/(2)g(t - 1.02)^2

so now we have

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Plz answer will give Brainliest answer to whoever does.

Answers

Answer:

  • A foot kicking a ball
  • A iPhone/phone being charged

Explanation:

A foot kicking a ball:

Potential energy is converted to kinetic energy.

A iPhone/Phone being charged:

Electrical energy is converted to chemical energy.

Answer:

A foot kicking ball.

An iPhone being charged

Explanation:

  • A foot kicking a ball is example of transportation of Kinetic energy

\n \sf\longmapsto K.E=(1)/(2)mv^2

  • An iPhone being charged means the electronic energy is converted into machinery energy

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F=
M=
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Answers

F=147N;

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Mass=15kg

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Answers

C. the rate at which work is done. hope i helped!
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