Idon't understand these following questions, can someone me?
1) find the work done by a 25 n force applied for 6 meters
2) calculate the potential energy of a 5 kg object sitting on a 3 m ledge
3) a rock is at the top of a 20 meter tall hill, the rock has a mass of 10 kg. how much potential energy does it have?

These questions are testing to see if you know
the formulas for work and potential energy ... or
if you know where to find them when you need them.

1).  The formula for work is:

                       Work = (force) x (distance) .

In this question:  Work = (25 N) x (6 m) = 160 joules .


The formula for potential energy is

                   PE  = (mass) x (gravity) x (height) .

On Earth, gravity = 9.8 m/s² 

This information gives you both of the other questions.

#2).  PE  = (mass) x (gravity) x (height)

               = (5 kg) x (9.8 m/s²) x (3m) =  147 joules

#3).  PE  = (mass) x (gravity) x (height)

               = (10 kg) x (9.8 m/s²) x (20 m) =  1,960 joules

Iwould think it is temperature, silica, oxides (gases)