Answer:
13.23J
Explanation:
PE = m*g*h
PE = (3 kg ) * (9.8 m/s/s) * (0.45 m)
Explanation:
The gravitational force equation is the following:

Where:
G = Gravitational constant = 
m1 & m2 = the mass of two related objects
r = distance between the two related objects
The problem gives you everything you need to plug into the formula, except for the gravitational constant. Let me know if you need further clarification.
Answer:
The water molecule cannot escape, since the average velocity of the water molecules is less than one sixth of the escape velocity of venus.
Explanation:
The average speed of gas molecules is given by:

R is the gas constant, T is the temperature and M the molar mass of the gas.
We know that a water molecule has a mass that is 18 times that of a hydrogen atom:

So, we have:

The water molecule cannot escape, since the average velocity of the water molecules is less than one sixth of the escape velocity of venus:

Gear because each spike is a wedge shape that adds a mechanical advatage