Hi, all.  Here are the rationale that I have given for some of the changes that I have made.

[b]Design Features[/b]

(1) Removal of  extra information like g (acceleration due to gravity) and R (normal force) and k (coefficient of friction)

Reduce cognitive load. Information not required for elementary school students

(2) Consistent colour scheme for concepts related to potential energy (PE) and kinetic energy (KE)

Signaling in the form of consistent colour scheme to guide the learners in organizing information (Mautone & Mayer, 2001).
Make the relationship between the related concepts more explicit to the students.

(3) Display of velocity information in symbolic (length of arrow) and numerical form near the object.
Spatial Continguity Effect related representations are placed close together  (Mayer, 2001). Allows the students to better visualize how the velocity changes as the height changes. 

(4) Representation of kinetic energy, potential energy and the total energy in numerical form.
Numerical representation complements the representation in bar chart.  (Multiple representation)

(5) Modification of Total Energy bar such that it is made up of KE and PE. Change the orientation of KE bar such that it is moving down

Spatial Contiguity  Effect  (Mayer, 2001)
Let the students better visualize that the total energy is made up of KE and PE and how KE and PE are related.