The location on the track where the train has the greatest potential energy is plzz?

This question is referring to potential energy, more specifically we can think about gravitational potential energy which we will call GPE. The formula for GPE is:

GPE = mgh

m = mass of substance
g = gravitational constant
h = height

Therefore, the GPE has a direct linear relationship with height. This suggests that as the height increases, so does the GPE. Now if we look at the image of the train, the train will have the greatest potential energy when it is at the top of the hill (the highest point). At the top of the hill the train will have the greatest height, and therefore, the greatest potential energy.

So the answer is the train has the greatest potential energy at position 1.

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.