Answer:
7 m/s
Explanation:
To solve this problem you must use the conservation of energy.

That math speak for, initial kinetic energy plus initial potential energy equals final kinetic energy plus final potential energy.
The initial PE (potential energy) is 0 because it hasn't been raised in the air yet. The final KE (kinetic energy) is 0 because it isn't moving. This gives the following:


K1=U2

Solve for v

Input known values and you get 7 m/s.
Potential energy is the answer
Answer:
c) 
Explanation:
Coulomb's law says that the force exerted between two charges is inversely proportional to the square of distance between them, and is given by the expression:

where k is a proportionality constant with the value 
In this case
, so we have:

Solving the equation for q, we have:



Replacing the given values:


Answer:
The mantle exists above the crust of the earth
Answer:
720 V
Explanation:
Given that,
The number of turns in primary coil, N₁ = 60
The number of turns in secondary coil, N₂ = 360
The input rms voltage, V₁ = 120 V
We need to find the output rms voltage of the secondary coil
. The relation between number of turns in primary coil - secondary coil to the input rms voltage to the output rms voltage is given by :

<h3>So, the output rms voltage of the secondary coil is 720 V. Hence, the correct option is (b).</h3>