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Answer:Radiation-3,Conduction-1,Convection-2</h2>
Explanation:
Radiation is the transfer of heat through electromagnetic waves.
These waves do not require any medium.This is the way we get heat from sun.Radiation is the quickest mode to transfer of heat.
Conduction is the transfer of heat through collisions of atomic particles.
This phenomenon largely occurs in solids like metals.The neighbour atoms sets the atoms into random motion thereby raising the temperature.
Convection is the transfer of heat through actual movement of medium particle.
This phenomenon occurs in gases an liquids.The medium particles actually traverse through the space transferring the heat.
We have that The Density and Volume is given as

The factors that affect Density are Mass and Volume
From the question we are told that
The piece of wood shown above has a mass of 20 grams.
Wood parameters
2cm
5cm
3cm
Generally the equation for the Volume is mathematically given as

Generally the equation for the Density is mathematically given as

Therefore the factors that affect Density are Mass and Volume
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Let vb be the velocity of the motorboat and let vs be the velocity of the stream.
We know that when she drives upstream the velocity is 8 m/s, in this scenario the velocities point in opposite directions, then we have the equations:

When she drives downstream the velocites point in the same direction then we have the equation:

hence we have the system of equations:

Solving the first equation for the velocity of the boat we have:

Plugging this in the second equation we have:

Therefore, the velocity of the stream is 2 m/s