According to the description given in the photo, the attached figure represents the problem graphically for the Atwood machine.
To solve this problem we must apply the concept related to the conservation of energy theorem.
PART A ) For energy conservation the initial kinetic and potential energy will be the same as the final kinetic and potential energy, so



PART B) Replacing the values given as,




Therefore the speed of the masses would be 1.8486m/s
The amount of heat needed to increase the temperature of a substance by

is given by

where m is the mass of the substance, Cs is its specific heat capacity and

is the increase of temperature.
If we re-arrange the formula, we get

And if we plug the data of the problem into the equation, we can find the specific heat capacity of the substance:
Answer:
Explanation:
F = kQq/r²
r = √(kQq/F)
a) r = √(8.899(10⁹)(8)(4) / 18(10¹³)) = 0.0397749... m
r = 40 mm
b) r = √(8.899(10⁹)(12)(3) / 18(10¹³)) = 0.0421876... m
r = 42 mm