Good lesson， well epaixlned， with good， friendly vocal presentation. Ratio triangles can also be quite useful for this introductory topic only. The equals ( = ) sign does not come out well with the computer graphics. I notice negative indices are not used at this stage， namely m/s^2 is used rather than ms^(-2). I guess that is also fine for an introduction. Seeing that you have had no responses so far， I’m hoping to have done you a favour by posting the first. Keep up the good work. Regards， Rick Swan.