A. The IV is the temperature of gas in the balloon.
B. The DV is the volume of the balloon.
This is because the temperature of the gas is the variable being manipulated in the experiment (Independent) and the volume is changing based on the shifts of the temperature (thus volume is Dependent).
Sound level at distance of 15 m is given as 20 dB
so intensity at this distance is given as



now if we move closer to some some distance the sound level is now 50 dB
now the intensity is given as



now we know that



so now the distance from friend must be 47 cm
The answer is <span>B. the amount of hot soup contained in a bowl. Buoyancy is defined as the upward force exerted by a fluid on an object immersed in that fluid. Buoyancy and density are two factors that affect the downward and upward forces exerted on object that affect its ability to "float" or "sink". Only B does not have anything to do with such forces.</span>
To solve the exercise it is necessary to apply the equations necessary to apply Newton's second law and the concept related to frictional force.
An angle of 30 degrees is formed on the vertical at an applied force of 2.3N
In this way the frictional force, opposite to the movement will be given by

where,
Kinetic friction constant
N = Normal Force (Mass*gravity)
The friction force is completely vertical and opposes the rising force of 2.3 N. The Normal force acts perpendicular to the surface (vertical) therefore corresponds to the horizontal component of the applied force.
The ascending force would be given by

As the block is moving upward, the friction force acts downward, also its weight acts downward. We can have


Considering the horizontal force the normal force on the block must be balanced by the horizontal component of pishing foce


Then the frictional force




Therefore the coefficient of kinetic friction is 0.26