Two astronauts are 1.40 m apart in their spaceship. One speaks to the other. The conversation is transmitted to earth via electromagnetic waves. The time it takes for sound waves to travel at 328 m/s through the air between the astronauts equals the time it takes for the electromagnetic waves to travel to the earth. How far away from the earth is the spaceship?

The spaceship is placed at a distance of meters from the Earth.

Explanation:

Distance between two astronauts, d = 1.4 m  

The time it takes for sound waves to travel at 328 m/s through the air between the astronauts equals the time it takes for the electromagnetic waves to travel to the earth.

For sound, time taken is given by :

For electromagnetic wave, time taken to travel the Earth is :

d is the distance from the Earth to the spaceship.

As time are same :

So, the spaceship is placed at a distance of meters from the Earth.

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.