The circumference of a circle is (pi) x (diameter)
The circumference of the cupcake is (pi) x (5 cm)
Halfway around is (1/2) x (pi) x (5 cm) = (2.5 pi cm) = <em>about 7.85 cm</em>
The 'why' appears up above, in the first 2 lines of this solution.
Better technology is helping us because we can see more stuff like the microscope we able to make assumptions based on what we saw.
The heat released by the water when it cools down by a temperature difference

is

where
m=432 g is the mass of the water

is the specific heat capacity of water

is the decrease of temperature of the water
Plugging the numbers into the equation, we find

and this is the amount of heat released by the water.
The size of the force varies inversely as the square of the distance between the two charges. Therefore, if the distance between the two charges is doubled, the attraction or repulsion becomes weaker, decreasing to one-fourth of the original value.