The first law of thermodynamics can be written as

where

is the variation of internal energy of the system

is the amount of heat absorbed by the system

is the work done by the system on the surrounding.
Using this form, the sign convention for Q and W becomes:
Q > 0 --> heat absorbed by the system (because it increases the internal energy)
Q < 0 --> heat released by the system (because it decreases the internal energy)
W > 0 --> work done by the system (for instance, an expansion: when the system expands, it does work on the surrounding, and so the internal energy decreases, this is why there is a negative sign in the formula Q-W)
W < 0 --> work done by the surrounding on the system (for instance, a compression: when the system is compressed, the surrounding is doing work on the system, and so the internal energy of the system increases)
Answer:
mgh₁ + ½mv₁² = mgh₂ + ½mv₂²
Explanation:
Initial total energy = final total energy
PE₁ + KE₁ = PE₂ + KE₂
mgh₁ + ½mv₁² = mgh₂ + ½mv₂²
Answer:

Explanation:
When the car is under an accelerating force and hits a tree, the instant force received by the tree is the same force that is accelerating the car.
The accelerating force can be calculated using Newton's second law:

Where m is the mass of the car and a is the acceleration.


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Answer:</h2>
<u>A. A nuclear power plant</u> produces radioactive wave.
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Explanation:</h2>
A plant in which a nuclear reactor is used as a source to produce heat is known as nuclear power plant. The heat formed by the reactor is used to form steam which can be used to drive turbines to produce electricity.
The coolant in reactor gets heated by the fission process taking place in the reactor. It is a cyclic process where the steam is condensed and reverted back. A nuclear power plant in active condition produce a small amount of radiation which can be sensed within a radius of 50 miles.