Air spaces are used in insulation because air is a poor conductor.
C) light waves travel faster than sound waves
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Complete Question
The complete question is shown on the first uploaded image
Answer:
a
The torque produced by the pile of rocks is
b
The distance of the single for equilibrium to occur is
Explanation:
From the question we are told that
The mass of the left rock is 
The mass of the rock on the right 
The distance from fulcrum to the center of the pile of rocks is 
Generally the torque produced by the pile of rock is mathematically represented as

Substituting values
Generally we can mathematically evaluated the distance of the the single rock that would put the system in equilibrium as follows
The torque due to the single rock is

At equilibrium the both torque are equal

Making
the subject of the formula

Substituting values
The scientific method. When conducting research, scientists use the scientific method to collect measurable, empirical evidence in an experiment related to a hypothesis (often in the form of an if/then statement), the results aiming to support or contradict a theory.
Answer:
The vector magnitudes F and r are always postive, so the sign o W is determined entirely by the angle e between the force and the displacement.Submit Figure 1 off 1 part C