What is the most effective way to clean the science desks?

Hypothesis:

How does the electric potential energy between two charged particles change if one particle is reduced by a factor of 3? a. increased by a factor of 3 b. it is decreased by a factor of 9 c. it is reduced by a factor of 3 d. it is increased by a factor of 9

50 points to who answers this question in a clear and simple explanation : to what hight will a mass of weight of 500 n be raised in 20 seconds by a motor using 4kw of power?

On his honeymoon, james joule attempted to explore the relationships between various forms of energy by measuring the rise of temperature of water which had fallen down a waterfall on mount blanc. what maximum temperature rise would one expect for a waterfall with a vertical drop of 20 m? the specific heat of water is 4186 j/kg ∙ k. a)0.064 c° b)0.053 c° c)0.071 c° d)0.047 c°